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WATANABE, Kimiko, Satsuki TOMIOKA, Kiyoko TANIMURA, Hisae OKU, and Koichiro ISOI. "Uptake of AMP, ADP, and ATP inEscherichia coliW." Bioscience, Biotechnology, and Biochemistry 75, no. 1 (January 23, 2011): 7–12. http://dx.doi.org/10.1271/bbb.100063.
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Schultz, V., I. Sussman, K. Bokvist, and K. Tornheim. "Bioluminometric Assay of ADP and ATP at High ATP/ADP Ratios: Assay of ADP After Enzymatic Removal of ATP." Analytical Biochemistry 215, no. 2 (December 1993): 302–4. http://dx.doi.org/10.1006/abio.1993.1591.
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Schulte, P. M., C. D. Moyes, and P. W. Hochachka. "Integrating metabolic pathways in post-exercise recovery of white muscle." Journal of Experimental Biology 166, no. 1 (May 1, 1992): 181–95. http://dx.doi.org/10.1242/jeb.166.1.181.
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Purine nucleotides (ATP, ADP, AMP, IMP), creatine, phosphocreatine, lactate, pyruvate and glycogen were measured in rainbow trout (Oncorhynchus mykiss) white muscle following exercise to exhaustion. Estimates of intracellular pH permitted calculation of free concentrations of nucleotides ([nucleotide]f) required for most models of control of energy metabolism. Creatine charge, [PCr]/([PCr]+[Cr]), fell from 0.49 +/− 0.05 (mean +/− S.E.M.) to 0.08 +/− 0.02 with exercise but recovered completely by the first sample (2 h). Although [ATP] declined to 24% of resting levels and recovered very slowly, RATP, [ATP]/([ATP]+[ADP]f+[AMP]f), and energy charge, EC, ([ATP]+0.5[ADP]f)/([ATP]+[ADP]f+[AMP]f), recovered as quickly as creatine charge. Changes in [IMP] mirrored those in [ATP], suggesting that AMP deaminase is responsible for maintaining RATP and EC. Recovery of carbon status was much slower than recovery of energy status. Lactate increased from 4 mumol g-1 at rest to 40 mumol g-1 at exhaustion and did not recover for more than 8 h. Glycogen depletion and resynthesis followed a similar time course. During the early stages of recovery, calculated [ADP]f declined by more than 10-fold relative to the resting values. The resulting high [ATP]/[ADP]f ratios may limit the rate at which white muscle mitochondria can produce ATP to fuel glycogenesis in situ. It is postulated that the high [ATP]/[ADP]f ratios are required to drive pyruvate kinase in the reverse direction for glyconeogenesis in recovery.
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Duval, M., A. R. Beaudoin, G. Bkaily, F. P. Gendron, and P. D'Orléans-Juste. "Characterization of the NTPDase activities in the mesentery pre- and post-capillary circuits of the guinea pig." Canadian Journal of Physiology and Pharmacology 81, no. 3 (March 1, 2003): 212–19. http://dx.doi.org/10.1139/y03-043.
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NTPDase is one of the principal enzymes involved in the sequential hydrolysis of ATP. In the present study, the presence and functionality of NTPDase in the mesenteric vein and artery were examined. Adenosine triphosphate (ATP) (0.011000 pmol) induces a dose-dependent vasodilation in the isolated arterial and venous mesenteric vasculatures of the guinea pig. Adenosine diphosphate (ADP) (0.011000 pmol) but not adenosine monophosphate (AMP) (0.011000 pmol) induces a similar response in the mesenteric vascular circuit. L-NAME, a nitric oxide synthase inhibitor (200 µM, 30 min), significantly reduces the arterial dilatory effect of ATP and abolishes the responses to ADP and AMP. Complete removal of the endothelium with 3-[(3-cholamidopropyl) dimethylammonio]-1-propansulfonate (CHAPS) (20 mM, 2 × 45 s) abolishes ATP-induced responses. Infusion of ATP in the vascular circuit generated detectable amounts of ADP and AMP, as measured by HPLC. CHAPS treatment significantly reduced the level of ATP and the production of AMP in the arterial mesenteric circuit. In contrast to the arterial mesenteric vasculature, endothelium removal in the venous circuit triggered a marked potentiation of ADP release and, interestingly, a marked reduction in the release of AMP. Moreover, a specific inhibitor of NTP diphosphohydrolase, 1-hydroxynaphthlene-3,6-disulfonic acid BGO 136 (10 mM for 20 min), significatively reduced AMP production in both vascular preparations. These results confirm that the endothelium contributes to the vasoactive properties of ATP, ADP, and AMP. Our data also demonstrated a significant role of endothelium in NTPDase activity on ADP and AMP production prior to exogenous administration of ATP. The activity of this particular enzyme appears to be different from the reaction products viewpoint (i.e., the production of ADP) in the pre- and post-mesenteric circuits, suggesting two different isoforms with different substrate specificities.Key words: ATP, ADP, AMP, NTPDase, mesenteric vasculature.
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BAKKE, MIKIO, and SHIGEYA SUZUKI. "Development of a Novel Hygiene Monitoring System Based on the Detection of Total Adenylate (ATP+ADP+AMP)." Journal of Food Protection 81, no. 5 (April 3, 2018): 729–37. http://dx.doi.org/10.4315/0362-028x.jfp-17-432.
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ABSTRACT ATP is the universal energy molecule found in animals, plants, and microorganisms. ATP rapid hygiene monitoring tests have been employed in the food industry to ensure that adequate cleanliness is being maintained. However, because ATP is hydrolyzed to ADP and AMP by metabolic processes, by heat treatment, or under acidic or alkaline conditions, total adenylate (ATP+ADP+AMP [A3]) could be a more reliable sanitation indicator of food residues that may cause biofilm formation and allergen contamination. Therefore, a novel hygiene monitoring system to measure A3 was developed based on the luciferin-luciferase assay with the combination of two enzymes, pyruvate kinase and pyruvate phosphate dikinase, that can convert ADP into ATP and recycle AMP into ATP, respectively. The newly developed A3 assay system afforded stable bioluminescence signals and equivalent linear calibration curves between relative light units (RLU) and the amounts of ATP, ADP, and AMP, respectively. To verify the significance of the A3 method, the ratios of ATP, ADP, and AMP in various food samples were determined; large amounts of ADP and AMP were found in a variety of foods, such as meat, seafood, dairy, nuts, fruits, vegetables, and fermented foods. Sanitation monitoring of stainless steel exposed to raw meat was also examined, and the A3 method achieved a 200-RLU level, the typical benchmark value, after complete washing with detergent and rinsing. In contrast, a conventional ATP method showed less than 200 RLU after only a light cold and hot water rinse. In conclusion, the A3 assay appeared to be suitable for detection of adenylates from food residues that are not detected by the conventional ATP assay.
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Resnick, Sol M., and Alexander J. B. Zehnder. "In Vitro ATP Regeneration from Polyphosphate and AMP by Polyphosphate:AMP Phosphotransferase and Adenylate Kinase from Acinetobacter johnsonii 210A." Applied and Environmental Microbiology 66, no. 5 (May 1, 2000): 2045–51. http://dx.doi.org/10.1128/aem.66.5.2045-2051.2000.
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ABSTRACT In vitro enzyme-based ATP regeneration systems are important for improving yields of ATP-dependent enzymatic reactions for preparative organic synthesis and biocatalysis. Several enzymatic ATP regeneration systems have been described but have some disadvantages. We report here on the use of polyphosphate:AMP phosphotransferase (PPT) fromAcinetobacter johnsonii strain 210A in an ATP regeneration system based on the use of polyphosphate (polyP) and AMP as substrates. We have examined the substrate specificity of PPT and demonstrated ATP regeneration from AMP and polyP using firefly luciferase and hexokinase as model ATP-requiring enzymes. PPT catalyzes the reaction polyP n + AMP → ADP + polyP n−1. The ADP can be converted to ATP by adenylate kinase (AdK). Substrate specificity with nucleoside and 2′-deoxynucleoside monophosphates was examined using partially purified PPT by measuring the formation of nucleoside diphosphates with high-pressure liquid chromatography. AMP and 2′-dAMP were efficiently phosphorylated to ADP and 2′-dADP, respectively. GMP, UMP, CMP, and IMP were not converted to the corresponding diphosphates at significant rates. Sufficient AdK and PPT activity in A. johnsonii 210A cell extract allowed demonstration of polyP-dependent ATP regeneration using a firefly luciferase-based ATP assay. Bioluminescence from the luciferase reaction, which normally decays very rapidly, was sustained in the presence of A. johnsonii 210A cell extract, MgCl2, polyP n=35, and AMP. Similar reaction mixtures containing strain 210A cell extract or partially purified PPT, polyP, AMP, glucose, and hexokinase formed glucose 6-phosphate. The results indicate that PPT from A. johnsonii is specific for AMP and 2′-dAMP and catalyzes a key reaction in the cell-free regeneration of ATP from AMP and polyP. The PPT/AdK system provides an alternative to existing enzymatic ATP regeneration systems in which phosphoenolpyruvate and acetylphosphate serve as phosphoryl donors and has the advantage that AMP and polyP are stabile, inexpensive substrates.
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Vetri, Francesco, Haoliang Xu, Lizhen Mao, Chanannait Paisansathan, and Dale A. Pelligrino. "ATP hydrolysis pathways and their contributions to pial arteriolar dilation in rats." American Journal of Physiology-Heart and Circulatory Physiology 301, no. 4 (October 2011): H1369—H1377. http://dx.doi.org/10.1152/ajpheart.00556.2011.
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ATP is thought to be released to the extracellular compartment by neurons and astrocytes during neural activation. We examined whether ATP exerts its effect of promoting pial arteriolar dilation (PAD) directly or upon conversion (via ecto-nucleotidase action) to AMP and adenosine. Blockade of extracellular direct ATP to AMP conversion, with ARL-67156, significantly reduced sciatic nerve stimulation-evoked PADs by 68%. We then monitored PADs during suffusions of ATP, ADP, AMP, and adenosine in the presence and absence of the following: 1) the ecto-5′-nucleotidase inhibitor α,β-methylene adenosine 5′-diphosphate (AOPCP), 2) the A2 receptor blocker ZM 241385, 3) the ADP P2Y1 receptor antagonist MRS 2179, and 4) ARL-67156. Vasodilations induced by 1 and 10 μM, but not 100 μM, ATP were markedly attenuated by ZM 241385, AOPCP, and ARL-67156. Substantial loss of reactivity to 100 μM ATP required coapplications of ZM 241385 and MRS 2179. Dilations induced by ADP were blocked by MRS 2179 but were not affected by either ZM 241385 or AOPCP. AMP-elicited dilation was partially inhibited by AOPCP and completely abolished by ZM 241385. Collectively, these and previous results indicate that extracellular ATP-derived adenosine and AMP, via A2 receptors, play key roles in neural activation-evoked PAD. However, at high extracellular ATP levels, some conversion to ADP may occur and contribute to PAD through P2Y1 activation.
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Chen, G., and H. Suzuki. "Endothelium-dependent hyperpolarization elicited by adenine compounds in rabbit carotid artery." American Journal of Physiology-Heart and Circulatory Physiology 260, no. 4 (April 1, 1991): H1037—H1042. http://dx.doi.org/10.1152/ajpheart.1991.260.4.h1037.
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Electrical responses of the membrane of intimal and adventitial smooth muscle cells of the rabbit carotid artery to ATP, ADP, AMP, and adenosine were recorded. In intimal cells, these compounds hyperpolarized the membrane. Mechanical removal of the endothelium altered the responses to ATP and ADP to one of a transient depolarization, with no alteration of the response to AMP and adenosine. In the adventitial cells, ATP and ADP produced a transient depolarization, whereas AMP and adenosine produced a sustained hyperpolarization, irrespective of the presence or absence of the endothelium. In tissues with an intact endothelium, 5'-adenylylimidodiphosphate tetralithium salt and alpha,beta-methylene ATP (mATP) transiently depolarized the membrane in these smooth muscles. In case of stabilization with mATP, only hyperpolarization was generated by ATP, in an endothelium-dependent manner. Our interpretation of these observations is that 1) ATP and ADP depolarize smooth muscle membrane by a direct action and hyperpolarize the membrane indirectly through the release of endothelium-derived hyperpolarizing factor, 2) AMP and adenosine hyperpolarize the membrane, independently of the endothelium, and 3) ATP receptors present on the endothelial cell membrane differ from those on smooth muscle membrane.
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Warburton, D., S. Buckley, and L. Cosico. "P1 and P2 purinergic receptor signal transduction in rat type II pneumocytes." Journal of Applied Physiology 66, no. 2 (February 1, 1989): 901–5. http://dx.doi.org/10.1152/jappl.1989.66.2.901.
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Extracellular ATP is a potent agonist of surfactant phosphatidylcholine (PC) exocytosis from type II pneumocytes in culture. We studied P1 and P2 receptor signal transduction in type II pneumocytes. The EC50 for ATP on PC exocytosis was 10(-6) M, whereas the EC50 for ADP, AMP, adenosine, and the nonmetabolizable ATP analogue alpha,beta-methylene ATP was 10(-4) M. The rank order of agonists for PC exocytosis was ATP greater than ADP greater than AMP greater than adenosine greater than alpha,beta-methylene ATP. The rank order of agonists for phosphatidylinositol (PI) hydrolysis was ATP greater than ADP, whereas AMP, adenosine, and alpha,beta-methylene ATP did not stimulate PI hydrolysis. ATP (10(-4) M) caused a 15-fold increase in adenosine 3′,5′-cyclic monophosphate (cAMP) production, and the nonmetabolizable adenosine analogue 5′-N-ethylcarboxyamidoadenosine (10(-6) M) increased cAMP production threefold. The effects of both these agonists on cAMP production were completely inhibited by the adenosine antagonist 8-phenyltheophylline (10(-5) M). The effects of ATP (10(-4) M) on PC exocytosis were inhibited 38% by 10(-5) M 8-phenyltheophylline. Thus, ATP regulates PC exocytosis by activating P2 receptors, which stimulate PI hydrolysis to inositol phosphate, as well as by activating P1 receptors, which stimulate cAMP production. Interactions between the P1 and P2 pathways may explain the high potency of extracellular ATP as an agonist of PC exocytosis.
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Ko, W. H., J. J. O'Dowd, J. D. Pediani, D. L. Bovell, H. Y. Elder, D. M. Jenkinson, and S. M. Wilson. "Extracellular ATP can activate autonomic signal transduction pathways in cultured equine sweat gland epithelial cells." Journal of Experimental Biology 190, no. 1 (May 1, 1994): 239–52. http://dx.doi.org/10.1242/jeb.190.1.239.
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Changes in intracellular free calcium concentration ([Ca2+]i) were monitored in a cell line that was derived from the equine sweat gland epithelium. ATP and closely related compounds could increase [Ca2+]i with a rank order of potency of UTP > or = ATP > ADP > AMP = adenosine = alpha,beta-methylene-ATP. The responses to ATP and to UTP were initiated by the release of calcium from an internal store and subsequently sustained by calcium influx. The rise in [Ca2+]i thus seems to be mediated by P2U receptors that are coupled to phosphoinositidase C. Some desensitisation of this response developed during repeated stimulation with ATP and this was blocked by staurosporine, an inhibitor of protein kinase C, and augmented by a phorbol ester which acts as an exogenous activator of this enzyme. A protein-kinase-C-dependent inhibitory pathway thus seems to become active during repeated stimulation with ATP. ATP and related compounds could also raise cellular cyclic AMP content. The order of potency was ATP > ADP = AMP = adenosine > UTP, suggesting that this response is mediated via a separate subclass of P2 receptor. The present results demonstrate that ATP can activate autonomic signal-transduction pathways in cultured equine sweat gland cells and suggest that there may be a purinergic component to the control of secretory activity in the equine sweat gland.
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Pinna, Silvana, Cäcilia Kunz, Aaron Halpern, Stuart A. Harrison, Sean F. Jordan, John Ward, Finn Werner, and Nick Lane. "A prebiotic basis for ATP as the universal energy currency." PLOS Biology 20, no. 10 (October 4, 2022): e3001437. http://dx.doi.org/10.1371/journal.pbio.3001437.
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ATP is universally conserved as the principal energy currency in cells, driving metabolism through phosphorylation and condensation reactions. Such deep conservation suggests that ATP arose at an early stage of biochemical evolution. Yet purine synthesis requires 6 phosphorylation steps linked to ATP hydrolysis. This autocatalytic requirement for ATP to synthesize ATP implies the need for an earlier prebiotic ATP equivalent, which could drive protometabolism before purine synthesis. Why this early phosphorylating agent was replaced, and specifically with ATP rather than other nucleoside triphosphates, remains a mystery. Here, we show that the deep conservation of ATP might reflect its prebiotic chemistry in relation to another universally conserved intermediate, acetyl phosphate (AcP), which bridges between thioester and phosphate metabolism by linking acetyl CoA to the substrate-level phosphorylation of ADP. We confirm earlier results showing that AcP can phosphorylate ADP to ATP at nearly 20% yield in water in the presence of Fe3+ ions. We then show that Fe3+ and AcP are surprisingly favoured. A wide range of prebiotically relevant ions and minerals failed to catalyse ADP phosphorylation. From a panel of prebiotic phosphorylating agents, only AcP, and to a lesser extent carbamoyl phosphate, showed any significant phosphorylating potential. Critically, AcP did not phosphorylate any other nucleoside diphosphate. We use these data, reaction kinetics, and molecular dynamic simulations to infer a possible mechanism. Our findings might suggest that the reason ATP is universally conserved across life is that its formation is chemically favoured in aqueous solution under mild prebiotic conditions.
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Li, Min-ji, Qin-ping Wei, Fu-tian Peng, Wen Yu, Jing-jing Luo, and Yong-fei Zhao. "Identification and Characterization of ATP/ADP Isopentenyltransferases (ATP/ADP PpIPTs) Genes in Peach." Journal of Plant Growth Regulation 38, no. 2 (August 30, 2018): 416–30. http://dx.doi.org/10.1007/s00344-018-9851-6.
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Meghji, P., J. D. Pearson, and L. L. Slakey. "Kinetics of extracellular ATP hydrolysis by microvascular endothelial cells from rat heart." Biochemical Journal 308, no. 3 (June 15, 1995): 725–31. http://dx.doi.org/10.1042/bj3080725.
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We have characterized the ectonucleotidases that catalyse the reaction sequence ATP-->ADP-->AMP-->adenosine on microvascular endothelial cells cultured from the rat heart. Computer simulation and data fitting of progress of reaction curves showed that depletion of substrate at the cell surface dominates the regulation of the rate of hydrolysis of ATP when it is presented to the cells. Preferential delivery of AMP by ADPase to 5′-nucleotidase makes a significant contribution to the regulation of adenosine production from ATP or ADP. By contrast, we found no evidence for the preferential delivery of ADP from ATPase to ADPase. Feed-forward inhibition of AMP hydrolysis by ADP and/or ATP also modulated the rate of adenosine production. The properties of the ectonucleotidases on rat heart microvascular cells are such that adenosine is produced at a steady rate over a wide range of ATP concentrations.
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Randak, Christoph O., Qian Dong, Amanda R. Ver Heul, Adrian H. Elcock, and Michael J. Welsh. "ATP and AMP Mutually Influence Their Interaction with the ATP-binding Cassette (ABC) Adenylate Kinase Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) at Separate Binding Sites." Journal of Biological Chemistry 288, no. 38 (August 6, 2013): 27692–701. http://dx.doi.org/10.1074/jbc.m113.479675.
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Cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel in the ATP-binding cassette (ABC) transporter protein family. In the presence of ATP and physiologically relevant concentrations of AMP, CFTR exhibits adenylate kinase activity (ATP + AMP ⇆ 2 ADP). Previous studies suggested that the interaction of nucleotide triphosphate with CFTR at ATP-binding site 2 is required for this activity. Two other ABC proteins, Rad50 and a structural maintenance of chromosome protein, also have adenylate kinase activity. All three ABC adenylate kinases bind and hydrolyze ATP in the absence of other nucleotides. However, little is known about how an ABC adenylate kinase interacts with ATP and AMP when both are present. Based on data from non-ABC adenylate kinases, we hypothesized that ATP and AMP mutually influence their interaction with CFTR at separate binding sites. We further hypothesized that only one of the two CFTR ATP-binding sites is involved in the adenylate kinase reaction. We found that 8-azidoadenosine 5′-triphosphate (8-N3-ATP) and 8-azidoadenosine 5′-monophosphate (8-N3-AMP) photolabeled separate sites in CFTR. Labeling of the AMP-binding site with 8-N3-AMP required the presence of ATP. Conversely, AMP enhanced photolabeling with 8-N3-ATP at ATP-binding site 2. The adenylate kinase active center probe P1,P5-di(adenosine-5′) pentaphosphate interacted simultaneously with an AMP-binding site and ATP-binding site 2. These results show that ATP and AMP interact with separate binding sites but mutually influence their interaction with the ABC adenylate kinase CFTR. They further indicate that the active center of the adenylate kinase comprises ATP-binding site 2.
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Hardie, D. Grahame. "Keeping the home fires burning: AMP-activated protein kinase." Journal of The Royal Society Interface 15, no. 138 (January 2018): 20170774. http://dx.doi.org/10.1098/rsif.2017.0774.
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Living cells obtain energy either by oxidizing reduced compounds of organic or mineral origin or by absorbing light. Whichever energy source is used, some of the energy released is conserved by converting adenosine diphosphate (ADP) to adenosine triphosphate (ATP), which are analogous to the chemicals in a rechargeable battery. The energy released by the conversion of ATP back to ADP is used to drive most energy-requiring processes, including cell growth, cell division, communication and movement. It is clearly essential to life that the production and consumption of ATP are always maintained in balance, and the AMP-activated protein kinase (AMPK) is one of the key cellular regulatory systems that ensures this. In eukaryotic cells (cells with nuclei and other internal membrane-bound structures, including human cells), most ATP is produced in mitochondria, which are thought to have been derived by the engulfment of oxidative bacteria by a host cell not previously able to use molecular oxygen. AMPK is activated by increasing AMP or ADP (AMP being generated from ADP whenever ADP rises) coupled with falling ATP. Relatives of AMPK are found in essentially all eukaryotes, and it may have evolved to allow the host cell to monitor the output of the newly acquired mitochondria and step their ATP production up or down according to the demand. Structural studies have illuminated how AMPK achieves the task of detecting small changes in AMP and ADP, despite the presence of much higher concentrations of ATP. Recently, it has been shown that AMPK can also sense the availability of glucose, the primary carbon source for most eukaryotic cells, via a mechanism independent of changes in AMP or ADP. Once activated by energy imbalance or glucose lack, AMPK modifies many target proteins by transferring phosphate groups to them from ATP. By this means, numerous ATP-producing processes are switched on (including the production of new mitochondria) and ATP-consuming processes are switched off, thus restoring energy homeostasis. Drugs that modulate AMPK have great potential in the treatment of metabolic disorders such as obesity and Type 2 diabetes, and even cancer. Indeed, some existing drugs such as metformin and aspirin, which were derived from traditional herbal remedies, appear to work, in part, by activating AMPK.
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Fleetwood, G., S. B. Coade, J. L. Gordon, and J. D. Pearson. "Kinetics of adenine nucleotide catabolism in coronary circulation of rats." American Journal of Physiology-Heart and Circulatory Physiology 256, no. 6 (June 1, 1989): H1565—H1572. http://dx.doi.org/10.1152/ajpheart.1989.256.6.h1565.
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We have used the rat isolated, perfused heart to study the metabolism of adenine nucleotides on a single passage through the coronary circulation. Low doses (3-30 nmol) of ATP, ADP, or AMP injected as a bolus were extensively catabolized by ectoenzymes. Increasing doses of each nucleotide demonstrated saturability of catabolism that occurred at significantly lower doses of AMP than of ADP or ATP. The patterns of catabolites formed in each case were consistent with the major pathway of metabolism being sequential dephosphorylation of ATP----ADP----AMP----adenosine, although from experiments in which [3H]ATP was co-injected with unlabeled ADP, it appears that some direct conversion of ATP----AMP can occur. Furthermore, particularly in the presence of excess unlabeled ATP, [3H]ADP was phosphorylated to [3H]ATP, indicating that ectoenzymes capable of interconverting nucleotides are present. By evaluating recovery and metabolism in serial samples collected rapidly after bolus injection, we were able to use the integrated form of the Michaelis-Menten equation as developed by Bronikowski et al. (Math. Biosci. 61: 237-266, 1982) to derive Michaelis constant (Km) and maximum velocity times capillary plasma volume (Amax) values for adenosinetriphosphatase, adenosine diphosphatase, and 5'-nucleotidase (450, 300, and 93 microM; and 5.3, 5.9, and 1.7 mumol/min, respectively). This analysis also indicated that there is a high degree of heterogeneity of path lengths within the coronary circulation.(ABSTRACT TRUNCATED AT 250 WORDS)
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Gowans, Graeme J., and D. Grahame Hardie. "AMPK: a cellular energy sensor primarily regulated by AMP." Biochemical Society Transactions 42, no. 1 (January 23, 2014): 71–75. http://dx.doi.org/10.1042/bst20130244.
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AMPK (AMP-activated protein kinase) is a cellular energy sensor that monitors the ratio of AMP/ATP, and possibly also ADP/ATP, inside cells. Once activated by falling cellular energy levels, it acts to restore energy homoeostasis by switching on catabolic pathways that generate ATP, while switching off anabolic pathways and other processes consuming ATP. AMPK is switched on by increases in AMP via three mechanisms, all of which are antagonized by ATP: (i) promotion of phosphorylation of Thr172 by upstream activating kinases; (ii) inhibition of dephosphorylation of Thr172 by phosphatases; and (iii) allosteric activation of the phosphorylated kinase. Recently, it has been proposed that the first two mechanisms are also triggered by ADP, which might be the physiological signal rather than AMP, and that the third mechanism may not be physiologically significant. We have re-evaluated these questions, and found that only mechanism (ii) is mimicked by ADP, and that ADP is also less potent than AMP, which we still believe to be the primary signal. We have also provided evidence that mechanism (iii), i.e. allosteric activation by AMP, is a quantitatively significant mechanism in intact cells.
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Dho, S., K. Stewart, and J. K. Foskett. "Purinergic receptor activation of Cl- secretion in T84 cells." American Journal of Physiology-Cell Physiology 262, no. 1 (January 1, 1992): C67—C74. http://dx.doi.org/10.1152/ajpcell.1992.262.1.c67.
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The regulation by ATP of Cl- secretion in T84 cells grown on filters was investigated by measuring short-circuit current (Isc = net Cl- secretion). ATP (greater than or equal to 10 microM) added to the basolateral side markedly stimulated Isc both in the presence and absence of forskolin-activated Isc. Fluorescence microscopy of cells loaded with the Ca2+ indicator fura-2 showed that ATP stimulated a transient increase in intracellular free Ca2+ concentration [Ca2+]i. The augmentation of forskolin-stimulated Isc by ATP was at least partly caused by mobilization of Ca2+ from an internal store because prior depletion of the store using ionomycin prevented the response. The activity sequence for stimulation of Isc in the presence of forskolin was adenosine 5'-O-(3-thiotriphosphate) = 5'-adenylylimidodiphosphate (AMP-PNP) greater than ATP greater than ADP greater than AMP, suggesting the presence of a P2 purinergic receptor. Neither beta, gamma-methyleneadenosine 5'-triphosphate nor alpha, beta-methyleneadenosine 5'-triphosphate increased the Isc. Stimulation of Isc by ATP in the absence of forskolin was at least partly due to the breakdown of ATP to AMP and adenosine, which act at P1 receptors to stimulate Isc, since 1) inhibition of the ecto-phosphohydrolase 5'-nucleotidase by alpha, beta-methylene-ADP partially inhibited stimulation of Isc by ATP, 2) the adenosine receptor antagonists caffeine and 8-phenyltheophylline markedly inhibited the ATP-stimulated Isc, and 3) AMP-PNP, a weakly hydrolyzable analogue of ATP, caused a much smaller increase in Isc compared with ATP. Adenosine had no effect on [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)
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Mysin, I. E., I. Yu Popova, and A. A. Osipov. "The Mathematical Model of Disturbance of Energy Metabolism in Brain during Development of Neurodegenerative Diseases: A Proposed Mechanism of Cell Death." Mathematical Biology and Bioinformatics 13, no. 2 (December 27, 2018): 591–608. http://dx.doi.org/10.17537/2018.13.591.
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The paper presents a theoretical study of the failure of energy metabolism in nervous tissue on a detailed biophysical model of metabolic coupling between neurons and astrocytes under afferent stimulation simulating by the release of glutamate into the presynaptic cleft. The main result of the model study is the detection of the phenomenon of adenylate collapse, the essence of which is the irreversible drop of ATP concentration after reaching the critical threshold value. This effect occurs as a result of the reversing of the reaction catalyzed by adenylate kinase. At high ATP values, the reaction equilibrium is shifted towards the formation of ADP from ATP and AMP. When the threshold is reached, the equilibrium shifts in the opposite direction, i.e., the formation of AMP and ATP from ADP occurs. If this situation is accompanied by a high consumption of ATP, the entire pool of adenine nucleotides goes into AMP. However, AMP is not phosphorylated, unlike ADP in glycolysis and oxidative phosphorylation, so the system quickly comes to depletion of ATP. Thus, adenylate collapse can be a new mechanism of the selective cell death in the development of neurodegenerative diseases.
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VALERO, Edelmira, Ramón VARÓN, and Francisco GARCÍA-CARMONA. "Kinetics of a self-amplifying substrate cycle: ADP–ATP cycling assay." Biochemical Journal 350, no. 1 (August 9, 2000): 237–43. http://dx.doi.org/10.1042/bj3500237.
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A kinetic study of an ATP–ADP amplification cyclic system involving the enzymes adenylate kinase, pyruvate kinase and l-lactate dehydrogenase has been made. The stoichiometry of the cycle is 2:1, because two molecules of ADP are synthesized from one each of ATP and AMP, and one molecule of ADP is converted back into one of ATP at each turn of the cycle. This results in a continuous exponential increase in the concentrations of ATP and ADP in the reaction medium, according to the equations obtained. This is therefore a substrate cycle that amplifies itself, the cycling rate increasing continuously with time. The background signal of the reagent was reduced by using apyrase to degrade ATP and ADP in the reagent, permitting detection limits as low as 16pmol of ATP and/or ADP in a continuous spectrophotometric assay.
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Markaryan, Adam, Olga Zaborina, Vasu Punj, and A. M. Chakrabarty. "Adenylate Kinase as a Virulence Factor ofPseudomonas aeruginosa." Journal of Bacteriology 183, no. 11 (June 1, 2001): 3345–52. http://dx.doi.org/10.1128/jb.183.11.3345-3352.2001.
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ABSTRACT Adenylate kinase (AK; ATP:AMP phosphotransferase, EC 2.7.4.3 ) is a ubiquitous enzyme that contributes to the homeostasis of adenine nucleotides in eukaryotic and prokaryotic cells. AK catalyzes the reversible reaction Mg · ATP + AMP ↔ Mg · ADP + ADP. In this study we show that AK secreted by the pathogenic strains of Pseudomonas aeruginosa appears to play an important role in macrophage cell death. We purified and characterized AK from the growth medium of a cystic fibrosis isolate strain of P. aeruginosa 8821 and hyperproduced it as a fusion protein with glutathione S-transferase. We demonstrated enhanced macrophage cell death in the presence of both the secreted and recombinant purified AK and its substrates AMP plus ATP or ADP. These data suggested that AK converts its substrates to a mixture of AMP, ADP, and ATP, which are potentially more cytotoxic than ATP alone. In addition, we observed increased macrophage killing in the presence of AK and ATP alone. Since the presence of ATPase activity on the macrophages was confirmed in the present work, external macrophage-effluxed ATP is converted to ADP, which in turn can be transformed by AK into a cytotoxic mixture of three adenine nucleotides. Evidence is presented in this study that secreted AK was detected in macrophages during infection with P. aeruginosa. Thus, the possible role of secreted AK as a virulence factor is in producing and keeping an intact pool of toxic mixtures of AMP, ADP, and ATP, which allows P. aeruginosa to exert its full virulence.
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Meghji, P., J. D. Pearson, and L. L. Slakey. "Regulation of extracellular adenosine production by ectonucleotidases of adult rat ventricular myocytes." American Journal of Physiology-Heart and Circulatory Physiology 263, no. 1 (July 1, 1992): H40—H47. http://dx.doi.org/10.1152/ajpheart.1992.263.1.h40.
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We have investigated the kinetic properties of the extracellular reaction sequence ATP----ADP----AMP----adenosine catalyzed by ectonucleotidases at the surface of adult rat cardiac myocytes. Analysis of progress of reaction curves indicates that depletion of substrate at cell surfaces dominates the regulation of the rate of hydrolysis of ATP or of ADP when it is the initial substrate. Preferential delivery of intermediate products to be substrates at cell surfaces makes a significant contribution to the regulation of adenosine production from ATP or ADP. Preferential delivery has more impact on the delivery of ADP from adenosinetriphosphatase (ATPase) to adenosinediphosphatase (ADPase) than on delivery of AMP from ADPase to 5'-nucleotidase. At high initial ATP concentrations, feed-forward inhibition of AMP hydrolysis also modulates the rate of adenosine production. Taken together, the properties of the ectonucleotidases on the myocyte provide a milieu at the cell surface that tends to be poor in nucleotides, especially ATP and ADP (P2 purinoceptor agonists), and rich in adenosine (a P1 purinoceptor agonist) during periods of supply of extracellular nucleotides.
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Asensi, M., A. Lopez-Rodas, J. Sastre, J. Vina, and J. M. Estrela. "Inhibition of gluconeogenesis by extracellular ATP in isolated rat hepatocytes." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 261, no. 6 (December 1, 1991): R1522—R1526. http://dx.doi.org/10.1152/ajpregu.1991.261.6.r1522.
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The aim of this study was to determine the effect of externally added ATP on gluconeogenesis by isolated hepatocytes from starved rats. High concentrations of extracellular ATP inhibited gluconeogenesis from lactate and pyruvate but not from glycerol or fructose. This inhibition was associated with an increase in intracellular adenosine contents. ADP, AMP, or adenosine but not guanosine 5'triphosphate, inosine 5' triphosphate, or adenine also inhibited gluconeogenesis. alpha, beta-Methylene-ATP, a nonmetabolizable structural analogue of ATP, did not affect the rate of gluconeogenesis. Intracellular ATP levels were increased by externally added ATP or adenosine, but ATP-to-ADP ratios in the cytosolic and mitochondrial compartments were diminished. Malate and phosphoenolpyruvate contents were decreased by extracellular ATP or adenosine. Our results show that inhibition of gluconeogenesis by high levels of extracellular ATP may be mediated by adenosine derived from ATP catabolism at the plasma membrane.
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Popovic, Zvezdana, and Douglas M. Templeton. "Interaction of iron regulatory protein-1 (IRP-1) with ATP/ADP maintains a non-IRE-binding state." Biochemical Journal 430, no. 2 (August 13, 2010): 315–24. http://dx.doi.org/10.1042/bj20100111.
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In its aconitase-inactive form, IRP-1 (iron regulatory protein-1)/cytosolic aconitase binds to the IRE (iron-responsive element) of several mRNAs to effect post-transcriptional regulation. We have shown previously that IRP-1 has ATPase activity and that binding of ATP suppresses the IRP-1/IRE interaction. In the present study, we characterize the binding activity further. Binding is observed with both [α-32P]ATP and [α-32P]ADP, but not with [γ-32P]ATP. Recombinant IRP-1 binds approximately two molecules of ATP, and positive co-operativity is observed with a Hill coefficient of 1.67±0.36 (EC50=44 μM) commencing at 1 μM ATP. Similar characteristics are observed with both apoprotein and the aconitase form. On binding, ATP is hydrolysed to ADP, and similar binding parameters and co-operativity are seen with ADP, suggesting that ATP hydrolysis is not rate limiting in product formation. The non-hydrolysable analogue AMP-PNP (adenosine 5′-[β,γ-imido]triphosphate) does not induce co-operativity. Upon incubation of IRP-1 with increasing concentrations of ATP or ADP, the protein migrates more slowly on agarose gel electrophoresis, and there is a shift in the CD spectrum. In this new state, adenosine nucleotide binding is competed for by other nucleotides (CTP, GTP and AMP-PNP), although ATP and ADP, but not the other nucleotides, partially stabilize the protein against spontaneous loss of aconitase activity when incubated at 37 °C. A mutant IRP-1(C437S) lacking aconitase activity shows only one ATP-binding site and lacks co-operativity. It has increased IRE-binding capacity and lower ATPase activity (Km=75±17 nmol/min per mg of protein) compared with the wild-type protein (Km=147±48 nmol/min per mg of protein). Under normal cellular conditions, it is predicted that ATP/ADP will maintain IRP-1 in a non-IRE-binding state.
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Wilson, David F., and Franz M. Matschinsky. "Metabolic homeostasis: oxidative phosphorylation and the metabolic requirements of higher plants and animals." Journal of Applied Physiology 125, no. 4 (October 1, 2018): 1183–92. http://dx.doi.org/10.1152/japplphysiol.00352.2018.
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A model of oxidative phosphorylation and its regulation is presented, which is consistent with the experimental data on metabolism in higher plants and animals. The variables that provide real-time control of metabolic status are: intramitochondrial [NAD+]/[NADH], energy state ([ATP]/[ADP][Pi]), and local oxygen concentration ([O2]). ATP consumption and respiratory chain enzyme content are tissue specific (liver vs. heart muscle), and the latter is modulated by chronic alterations in ATP consumption (i.e., endurance training etc.). ATP consumption affects the energy state, which increases or decreases as necessary to match synthesis with consumption. [NAD+]/[NADH], local [O2], and respiratory chain content determine the energy state at which match of synthesis and utilization is achieved. Tissues vary widely in their ranges of ATP consumption. Expressed as the turnover of cytochrome c, the rates may change little (7 to 12/s) (liver) or a lot (1 to >300/s) (flight muscle of birds, bats, and insects). Ancillary metabolic pathways, including creatine or arginine kinase, glycerol phosphate shuttle, fatty acid, and citric acid cycle dehydrogenases, are responsible for meeting tissue-specific differences in maximal rate and range in ATP utilization without displacing metabolic homeostasis. Intramitochondrial [NAD+]/[NADH], [ATP], and [Pi] are adjusted to keep [ADP] and [AMP] similar for all tissues despite large differences in ranges in ATP utilization. This is essential because [ADP] and [AMP], particularly the latter, have major roles in regulating the activity of many enzymes and signaling pathways (AMP deaminase, AMP dependent protein kinases, etc.) common to all higher plants and animals. NEW & NOTEWORTHY Oxidative phosphorylation has an intrinsic program that sets and stabilizes cellular energy state ([ATP]/[ADP][Pi]), and thereby metabolic homeostasis. A computational model consistent with regulation of oxidative phosphorylation in higher plants and animals is presented. Focus is on metabolism ancillary to oxidative phosphorylation by which it was integrated into preexisting metabolic regulation and adapted by evolution to develop cells and tissues with differing rates of ATP utilization: i.e., liver versus brain versus muscle.
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Gough, N. R. "ADP for ATP Exchange Mechanism." Science's STKE 2007, no. 410 (October 30, 2007): tw392. http://dx.doi.org/10.1126/stke.4102007tw392.
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Kudryashov, Dmitri S., and Emil Reisler. "ATP and ADP actin states." Biopolymers 99, no. 4 (January 25, 2013): 245–56. http://dx.doi.org/10.1002/bip.22155.
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Katchanov, G., J. Xu, A. Clay, and A. Pelleg. "Electrophysiological-anatomic correlates of ATP-triggered vagal reflex in the dog. IV. Role of LV vagal afferents." American Journal of Physiology-Heart and Circulatory Physiology 272, no. 4 (April 1, 1997): H1898—H1903. http://dx.doi.org/10.1152/ajpheart.1997.272.4.h1898.
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The negative chronotropic action and the time to peak effect (t(p)) of ATP and its related analogs [2-methylthio-ATP (2-MeSATP), alpha,beta-methylene-ATP (alpha,beta-mATP), and beta,gamma-methylene-ATP (beta,gamma-mATP)] as well as ADP, AMP, and adenosine were determined in anesthetized dogs. Intra-right atrium (RA) and intra-left main coronary artery (LM) ATP markedly suppressed sinus node automaticity. ATP induced a much greater response when administered into the LM than into the RA. The t(p) of ATP administered at the former site was much shorter than that at the latter site. Intra-LM adenosine had either no effect or a relatively very small effect, and its t(p) was significantly longer than that of intra-LM ATP. Bilateral cervical vagotomy either abolished or markedly attenuated the effect of intra-RA and intra-LM ATP; under these conditions, the actions of ATP and adenosine and their t(p) values became similar. The structure-function cascade of intra-LM ATP and its analogs was alpha,beta-mATP > 2-MeSATP > ATP > or = beta,gamma-mATP > ADP >> AMP = 0. The P2X-purinoceptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid markedly attenuated the negative chronotropic action of all purine nucleotides. It was concluded that 1) ATP triggers a cardiocardiac vagal depressor reflex by stimulating vagal afferent nerve terminals in the LV myocardium and 2) this action is mediated by P2X-purinoceptors.
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Zhang, Haoling, Haolong Zhang, Rui Zhao, Doblin Sandai, Zhijing Song, Zhongwen Zhang, and Wei Wang. "ATP Cellotoxicity, ATP-Induced Cell Death and ATP Depletion." International Journal of Public Health and Medical Research 1, no. 2 (May 30, 2024): 35–38. http://dx.doi.org/10.62051/ijphmr.v1n2.05.
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This paper delves into three pivotal themes concerning adenosine triphosphate (ATP): ATP cytotoxicity, ATP-induced cell death, and ATP depletion. Initially, we scrutinize ATP's involvement in cytotoxicity, with a specific focus on elucidating the mechanisms underlying cell demise triggered by augmented extracellular ATP concentrations. Subsequently, we investigate the process of ATP-induced cell death, emphasizing the repercussions of heightened extracellular ATP levels on cellular dynamics and associated biological responses. Lastly, we probe the impact of ATP depletion on cellular function and contemplate the plausible manifestation of cell death resulting from ATP depletion. Through a comprehensive examination of these topics, a deeper understanding of ATP's multifaceted role in cellular biology emerges, offering novel insights and strategies for the treatment and prevention of related diseases.
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Buxton, D. B., S. M. Robertson, and M. S. Olson. "Stimulation of glycogenolysis by adenine nucleotides in the perfused rat liver." Biochemical Journal 237, no. 3 (August 1, 1986): 773–80. http://dx.doi.org/10.1042/bj2370773.
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Infusion of adenine nucleotides and adenosine into perfused rat livers resulted in stimulation of hepatic glycogenolysis, transient increases in the effluent perfusate [3-hydroxybutyrate]/[acetoacetate] ratio, and increased portal vein pressure. In livers perfused with buffer containing 50 microM-Ca2+, transient efflux of Ca2+ was seen on stimulation of the liver with adenine nucleotides or adenosine. ADP was the most potent of the nucleotides, stimulating glucose output at concentrations as low as 0.15 microM, with half-maximal stimulation at approx. 1 microM, and ATP was slightly less potent, half-maximal stimulation requiring 4 microM-ATP. AMP and adenosine were much less effective, doses giving half-maximal stimulation being 40 and 20 microM respectively. Non-hydrolysed ATP analogues were much less effective than ATP in promoting changes in hepatic metabolism. ITP, GTP and GDP caused similar changes in hepatic metabolism to ATP, but were 10-20 times less potent than ATP. In livers perfused at low (7 microM) Ca2+, infusion of phenylephrine before ATP desensitized hepatic responses to ATP. Repeated infusions of ATP in such low-Ca2+-perfused livers caused homologous desensitization of ATP responses, and also desensitized subsequent Ca2+-dependent responses to phenylephrine. A short infusion of Ca2+ (1.25 mM) after phenylephrine infusion restored subsequent responses to ATP, indicating that, during perfusion with buffer containing 7 microM-Ca2+, ATP and phenylephrine deplete the same pool of intracellular Ca2+, which can be rapidly replenished in the presence of extracellular Ca2+. Measurement of cyclic AMP in freeze-clamped liver tissue demonstrated that adenosine (150 microM) significantly increased hepatic cyclic AMP, whereas ATP (15 microM) was without effect. It is concluded that ATP and ADP stimulate hepatic glycogenolysis via P2-purinergic receptors, through a Ca2+-dependent mechanism similar to that in alpha-adrenergic stimulation of hepatic tissue. However, adenosine stimulates glycogenolysis via P1-purinoreceptors and/or uptake into the cell, at least partially through a mechanism involving increase in cyclic AMP. Further, the hepatic response to adenine nucleotides may be significant in regulating hepatic glucose output in physiological and pathophysiological states.
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Shanbhag, S. M., and G. R. Choppin. "Thermodynamics of Mg and Ca complexation with AMP, ADP, ATP." Inorganica Chimica Acta 138, no. 3 (December 1987): 187–92. http://dx.doi.org/10.1016/s0020-1693(00)81221-9.
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Hosseini, Mir Wais, and Jean-Marie Lehn. "Binding of AMP, ADP, and ATP Nucleotides by Polyammonium Macrocycles." Helvetica Chimica Acta 70, no. 5 (August 12, 1987): 1312–19. http://dx.doi.org/10.1002/hlca.19870700512.
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Weinreich, Frank, John R. Riordan, and Georg Nagel. "Dual Effects of Adp and Adenylylimidodiphosphate on Cftr Channel Kinetics Show Binding to Two Different Nucleotide Binding Sites." Journal of General Physiology 114, no. 1 (July 1, 1999): 55–70. http://dx.doi.org/10.1085/jgp.114.1.55.
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The CFTR chloride channel is regulated by phosphorylation by protein kinases, especially PKA, and by nucleotides interacting with the two nucleotide binding domains, NBD-A and NBD-B. Giant excised inside-out membrane patches from Xenopus oocytes expressing human epithelial cystic fibrosis transmembrane conductance regulator (CFTR) were tested for their chloride conductance in response to the application of PKA and nucleotides. Rapid changes in the concentration of ATP, its nonhydrolyzable analogue adenylylimidodiphosphate (AMP-PNP), its photolabile derivative ATP-P3-[1-(2-nitrophenyl)ethyl]ester, or ADP led to changes in chloride conductance with characteristic time constants, which reflected interaction of CFTR with these nucleotides. The conductance changes of strongly phosphorylated channels were slower than those of partially phosphorylated CFTR. AMP-PNP decelerated relaxations of conductance increase and decay, whereas ATP-P3-[1-(2-nitrophenyl)ethyl]ester only decelerated the conductance increase upon ATP addition. ADP decelerated the conductance increase upon ATP addition and accelerated the conductance decay upon ATP withdrawal. The results present the first direct evidence that AMP-PNP binds to two sites on the CFTR. The effects of ADP also suggest two different binding sites because of the two different modes of inhibition observed: it competes with ATP for binding (to NBD-A) on the closed channel, but it also binds to channels opened by ATP, which might either reflect binding to NBD-A (i.e., product inhibition in the hydrolysis cycle) or allosteric binding to NBD-B, which accelerates the hydrolysis cycle at NBD-A.
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SMITH, N. W., J. J. SINDELAR, and S. A. RANKIN. "Quantities of Adenylate Homologues (ATP+ADP+AMP) Change over Time in Prokaryotic and Eukaryotic Cells." Journal of Food Protection 82, no. 12 (November 13, 2019): 2088–93. http://dx.doi.org/10.4315/0362-028x.jfp-19-223.
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ABSTRACT Rapid assays for the assessment of the hygienic state of surfaces in food and medical industries include the use of technologies designed to detect the presence of the metabolite ATP. ATP is a critical metabolite and energy source for most living organisms; therefore, the presence of ATP can be an indicator of surface hygiene based on the presence of soil or food residues associated with inadequate cleaning. The concentrations of ATP vary based on an organism's metabolic state, thus potentially influencing the sensitivity of ATP-based assays. However, little has been published detailing the quantitative changes of ATP to the adenylate homologues ADP and AMP nor the quantitative and cumulative fate of these homologues over time as the metabolic state remains in flux. The objective of this study was to quantify the individual and cumulative (AXP) concentrations of these three adenylate homologues over defined time periods in selected eukaryotic tissue and prokaryotic cell cultures of significance to hygiene. ATP concentrations differed substantially across these selected variables of time and source. The 1- to 3-log reductions in ATP concentrations over time were highly affected by organism type. In general, ADP became the predominate adenylate in eukaryotic tissue, and AMP was the predominate adenylate in the prokaryotic cells at later time points in each study. Total AXP concentrations dropped in general, reflective primarily of the loss of ATP. The results of ATP-based techniques for hygiene surveillance will vary as a function of the amount of cellular material present and the metabolic state of such material. HIGHLIGHTS
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Bertrand, G., J. Chapal, and M. M. Loubatieres-Mariani. "Potentiating synergism between adenosine diphosphate or triphosphate and acetylcholine on insulin secretion." American Journal of Physiology-Endocrinology and Metabolism 251, no. 4 (October 1, 1986): E416—E421. http://dx.doi.org/10.1152/ajpendo.1986.251.4.e416.
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The interaction between adenosine di- or triphosphate (ADP or ATP) and acetylcholine (ACh) was studied on insulin secretion. The experiments were performed on the isolated perfused rat pancreas, in the presence of a physiological nonstimulating glucose concentration (5.5 mM). ADP or ATP (1.65 microM) and ACh (0.05 microM) elicited a comparable peak of insulin secretion. When either ATP or ADP was simultaneously infused with ACh, insulin secretory response was significantly higher than the sum of the responses of each agonist applied separately. Similar effects were obtained with stable structural analogues of ATP and ADP (adenylimidodiphosphate, AMP-PNP, and alpha, beta-methyleneadenosine 5'-diphosphate, alpha, beta-methylene ADP) whether they acted alone or in combination with ACh. In contrast, adenosine was ineffective. Furthermore, the study of combined half doses of ATP (or ADP) and ACh allowed us to establish a potentiating synergism between both agonists. These data indicate a potentiating synergism on the beta-cell between ACh and ATP or ADP, the substances acting, respectively, via muscarinic cholinergic receptors and purinergic P2 receptors. So, ATP and ADP by activating P2 receptors could be involved in the parasympathetic control of insulin secretion.
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Naito, Y., and J. M. Lowenstein. "5′-Nucleotidase from rat heart membranes. Inhibition by adenine nucleotides and related compounds." Biochemical Journal 226, no. 3 (March 15, 1985): 645–51. http://dx.doi.org/10.1042/bj2260645.
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ADP and ATP and their analogues were evaluated as inhibitors of 5′-nucleotidase purified from heart plasma membrane. ADP analogues are more powerful inhibitors than the corresponding ATP analogues. The most powerful inhibitor found is adenosine 5′-[alpha beta-methylene]diphosphate (AOPCP) for which the enzyme shows a Ki of 5 nM at pH 7.2. Measurements of pKi values for ADP and AOPCP as a function of pH indicate that the major inhibitory species of both nucleotides is the dianion. In the physiological range of pH values, AOPCP is a more powerful inhibitor than ADP principally because a higher percentage of AOPCP exists in the dianion form. The methylenephosphonate analogue of AMP (ACP), though not a substrate, is a moderately effective inhibitor. The corresponding analogues of ADP (ACPOP) and ATP (ACPOPOP) are as good inhibitors as ADP and ATP respectively. The thiophosphate analogues of ADP all inhibit 5′-nucleotidase, although not as powerfully as ADP, the most effective of these analogues being adenosine 5′-O-(1-thiodiphosphate) diastereoisomer B (ADP[alpha S](B)]. Other nucleotides inhibit the enzyme, but none is as effective as AOPCP. Inorganic tripolyphosphate and methylenediphosphonate are better inhibitors of the enzyme than is inorganic pyrophosphate. Inorganic thiophosphate is a better inhibitor than is orthophosphate. Hill plots of the ADP and AOPCP inhibition yield slopes close to 1; Hill plots of the ATP inhibition yield slopes of about 0.6. MgADP- is not an inhibitor, and MgATP2- is at best a very weak inhibitor of the enzyme.
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Gorman, Mark W., Kayoko Ogimoto, Margaret V. Savage, Kenneth A. Jacobson, and Eric O. Feigl. "Nucleotide coronary vasodilation in guinea pig hearts." American Journal of Physiology-Heart and Circulatory Physiology 285, no. 3 (September 2003): H1040—H1047. http://dx.doi.org/10.1152/ajpheart.00981.2002.
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The role of P1 receptors and P2Y1 receptors in coronary vasodilator responses to adenine nucleotides was examined in the isolated guinea pig heart. Bolus arterial injections of nucleotides were made in hearts perfused at constant pressure. Peak increase in flow was measured before and after addition of purinoceptor antagonists. Both the P1 receptor antagonist 8-( p-sulfophenyl)theophylline and adenosine deaminase inhibited adenosine vasodilation. AMP-induced vasodilation was inhibited by P1 receptor blockade but not by adenosine deaminase or by the selective P2Y1 antagonist N6-methyl-2′-deoxyadenosine 3′,5′-bisphosphate (MRS 2179). ADP-induced vasodilation was moderately inhibited by P1 receptor blockade and greatly inhibited by combined P1 and P2Y1 blockade. ATP-induced vasodilation was antagonized by P1 blockade but not by adenosine deaminase. Addition of P2Y1 blockade to P1 blockade shifted the ATP dose-response curve further rightward. It is concluded that in this preparation ATP-induced vasodilation results primarily from AMP stimulation of P1 receptors, with a smaller component from ATP or ADP acting on P2Y1 receptors. ADP-induced vasodilation is largely due to P2Y1 receptors, with a smaller contribution by AMP or adenosine acting via P1 receptors. AMP responses are mediated solely by P1 receptors. Adenosine contributes very little to vasodilation resulting from bolus intracoronary injections of ATP, ADP, or AMP.
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Hancock, Chad R., Jeffrey J. Brault, Robert W. Wiseman, Ronald L. Terjung, and Ronald A. Meyer. "31P-NMR observation of free ADP during fatiguing, repetitive contractions of murine skeletal muscle lacking AK1." American Journal of Physiology-Cell Physiology 288, no. 6 (June 2005): C1298—C1304. http://dx.doi.org/10.1152/ajpcell.00621.2004.
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Metabolic control within skeletal muscle is designed to limit ADP accumulation even during conditions where ATP demand is out of balance with ATP synthesis. This is accomplished by the reactions of adenylate kinase (AK; ADP+ADP ↔ AMP+ATP) and AMP deaminase (AMP+H2O → NH3+IMP), which limit ADP accumulation under these conditions. The purpose of this study was to determine whether AK deficiency (AK−/−) would result in sufficient ADP accumulation to be visible using 31P-NMRS during the high energy demands of frequent in situ tetanic contractions. To do this we examined the high-energy phosphates of the gastrocnemius muscle in the knockout mouse with AK1−/− and wild-type (WT) control muscle over the course of 64 rapid (2/s) isometric tetanic contractions. Near-complete depletion of phosphocreatine was apparent after 16 contractions in both groups. By ∼40 contractions, ADP was clearly visible in AK1−/− muscle. This transient concentration of the NMR visible free ADP was estimated to be ∼1.7 mM, and represents the first time free ADP has been directly measured in contracting skeletal muscle. Such an increase in free ADP is severalfold greater than previously thought to occur. This large accumulation of free ADP also represents a significant reduction in energy available from ATP, and has implications on cellular processes that depend on a high yield of energy from ATP such as calcium sequestration. Remarkably, the AK1−/− and WT muscles exhibited similar fatigue profiles. Our findings suggest that skeletal muscle is surprisingly tolerant to a large increase in ADP and by extension, a decline in energy from ATP.
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Rouse, D., M. Leite, and W. N. Suki. "ATP inhibits the hydrosmotic effect of AVP in rabbit CCT: evidence for a nucleotide P2u receptor." American Journal of Physiology-Renal Physiology 267, no. 2 (August 1, 1994): F289—F295. http://dx.doi.org/10.1152/ajprenal.1994.267.2.f289.
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In rabbit renal cortical collecting tubule (CCT), perfused in vitro at 38 degrees C, ATP in concentrations of 10(-7) M and greater inhibits arginine vasopressin (AVP)-stimulated osmotic water permeability (Pf). The P1-purinergic receptor antagonist 8-phenyltheophylline did not attenuate the inhibitory action of ATP, and the poorly hydrolyzable ATP analogue, 5'-adenylylimidodiphosphate (AMP-PNP), mimicked the effect of ATP, arguing against an effect of ATP on a P1 receptor or the "P site." Purinergic receptor agonists inhibited AVP-stimulated Pf with the following rank order efficacy: ATP = ADP = UTP = AMP-PNP = alpha, beta-methylene-ATP > 2-methylthio-ATP >> AMP > adenosine, consistent with the pharmacology of a "nucleotide" receptor subtype. Pertussis toxin pretreatment attenuated the action of 10(-5) and 10(-6) MATP; however, 10(-4) MATP failed to inhibit the hydrosmotic action of forskolin or 8-bromoadenosine 3',5'-cyclic monophosphate. Pretreatment with the phosphodiesterase inhibitor RO20-1724 or indomethacin did not inhibit the action of ATP. Staurosporin and 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester significantly attenuated the inhibition of Pf by lower concentrations of ATP. These data suggest that ATP activates nucleotide receptors on the CCT, mobilizing intracellular Ca2+, which inhibits the hydrosmotic action of AVP.
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Sarkis, J. J. F., J. A. Guimarães, and J. M. C. Ribeiro. "Salivary apyrase of Rhodnius prolixus. Kinetics and purification." Biochemical Journal 233, no. 3 (February 1, 1986): 885–91. http://dx.doi.org/10.1042/bj2330885.
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The salivary apyrase activity of the blood-sucking bug Rhodnius prolixus was found to reside in a true apyrase (ATP diphosphohydrolase, EC 3.6.1.5) enzyme. The crude saliva was devoid of 5′-nucleotidase, inorganic pyrophosphatase, phosphatase and adenylate kinase activities. ATP hydrolysis proceeded directly to AMP and Pi without significant accumulation of ADP. Km values for ATP and ADP hydrolysis were 229 and 291 microM respectively. Ki values for ATP and ADP inhibition of ADP and ATP hydrolysis were not different from the Km values, and these experiments indicated competitive inhibition. Activities were purified 126-fold by combined gel filtration and ion-exchange chromatography procedures with a yield of 63%. The purified enzyme displayed specific activities of 580 and 335 mumol of Pi released/min per mg of protein for ATP and ADP hydrolysis respectively. The action of the purified enzyme on several phosphate esters indicates that Rhodnius apyrase is a non-specific nucleosidetriphosphate diphosphohydrolase.
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Balazovich, K. J., and L. A. Boxer. "Extracellular adenosine nucleotides stimulate protein kinase C activity and human neutrophil activation." Journal of Immunology 144, no. 2 (January 15, 1990): 631–37. http://dx.doi.org/10.4049/jimmunol.144.2.631.
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Abstract We studied the effect of adenosine nucleotides on several aspects of the functional activation of human peripheral blood polymorphonuclear leukocytes (PMN). Radiolabeled ATP bound to PMN in a manner suggesting the existence of specific binding sites because: 1) binding was reversed (92 +/- 6%) by 100-fold excess concentrations of unlabeled ATP but minimally by either ADP (43 +/- 12%) or GTP (37 +/- 8%); and 2) binding saturation was achieved (i.e., specific binding did not increase) above 250 microM ATP. Binding studies revealed that significant ATP hydrolysis occurred, even at low temperatures and in the presence of phosphatase inhibitors. Adenosine nucleotides activated signal transduction mechanisms in PMN because: 1) 1 to 100 microM ATP and 5'-adenylylimidodiphosphate (AMP-PNP) stimulated increased production of 1,2-diacylglycerols; 2) ATP (0.5 to 500 microM) and ADP (0.1 to 10 mM) induced increased insoluble protein kinase (PKC) activity in a dose-dependent manner when used at concentrations greater than 50 microM; 3) ATP (greater than or equal to 50 microM) induced a shift in the solubility of phorbol receptors from mostly soluble (89% in untreated cells) to mostly insoluble (68%), whereas ADP, GTP, and GDP were effective at higher concentrations; and 4) greater than or equal to 50 microM ATP stimulated increased phosphorylation of endogenous PMN proteins. AMP-PNP induced PKC activity and phosphoprotein changes that were qualitatively similar to those observed when PMN were treated with ATP, suggesting that extracellular ATP hydrolysis is not required for signal transduction to activate PKC. Functionally, ATP stimulated the secretion of specific (but not azurophil) granules because vitamin B12-binding protein and low levels of lysozyme, but not beta-glucuronidase, were released; qualitatively similar results were obtained by using AMP-PNP. These results suggest that certain adenosine nucleotides employed at physiologically relevant concentrations stimulate increased 1,2-diacylglycerol production, PKC activity, granule secretion, and endogenous phosphoprotein formation in a manner that is independent of extracellular ATP hydrolysis.
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Sun, Tianjun, Koto Hayakawa, and Marie E. Fraser. "ADP–Mg2+bound to the ATP-grasp domain of ATP-citrate lyase." Acta Crystallographica Section F Structural Biology and Crystallization Communications 67, no. 10 (September 24, 2011): 1168–72. http://dx.doi.org/10.1107/s1744309111028363.
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Wang, W., and G. Giebisch. "Dual effect of adenosine triphosphate on the apical small conductance K+ channel of the rat cortical collecting duct." Journal of General Physiology 98, no. 1 (July 1, 1991): 35–61. http://dx.doi.org/10.1085/jgp.98.1.35.
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We used the patch-clamp technique to study the effects of ATP on the small-conductance potassium channel in the apical membrane of rat cortical collecting duct (CCD). This channel has a high open probability (0.96) in the cell-attached mode but activity frequently disappeared progressively within 1-10 min after channel excision (channel "run-down"). Two effects of ATP were observed. Using inside-out patches, low concentrations of ATP (0.05-0.1 mM) restored channel activity in the presence of cAMP-dependent protein kinase A (PKA). In contrast, high concentrations (1 mM) of adenosine triphosphate (ATP) reduced the open probability (Po) of the channel in inside-out patches from 0.96 to 0. 1.2 mM adenosine diphosphate (ADP) also blocked channel activity completely, but 2 mM adenosine 5'-[beta,gamma-imido]triphosphate (AMP-PNP), a nonhydrolyzable ATP analogue, reduced Po only from 0.96 to 0.87. The half-maximal inhibition (Ki) of ATP and ADP was 0.5 and 0.6 mM, respectively, and the Hill coefficient of both ATP and ADP was close to 3. Addition of 0.2 or 0.4 mM ADP shifted the Ki of ATP to 1.0 and 2.0 mM, respectively. ADP did not alter the Hill coefficient. Reduction of the bath pH from 7.4 to 7.2 reduced the Ki of ATP to 0.3 mM. In contrast, a decrease of the free Mg2+ concentration from 1.6 mM to 20 microM increased the Ki of ATP to 1.6 mM without changing the Hill coefficient; ADP was still able to relieve the ATP-induced inhibition of channel activity over this low range of free Mg2+ concentrations. The blocking effect of ATP on channel activity in inside-out patches could be attenuated by adding exogenous PKA catalytic subunit to the bath. The dual effects of ATP on the potassium channel can be explained by assuming that (a) ATP is a substrate for PKA that phosphorylates the potassium channel to maintain normal function. (b) High concentrations of ATP inhibit the channel activity; we propose that the ATP-induced blockade results from inhibition of PKA-induced channel phosphorylation.
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Murgo, AJ, JG Contrera, and FD Sistare. "Evidence for separate calcium-signaling P2T and P2U purinoceptors in human megakaryocytic Dami cells." Blood 83, no. 5 (March 1, 1994): 1258–67. http://dx.doi.org/10.1182/blood.v83.5.1258.1258.
Full textAbstract:
Abstract Recently (J Pharmacol Exp Ther 261:580, 1992), we have shown that K562 leukemia cells express a calcium-signaling purinoceptor with characteristics of the P2T receptor subtype for adenosine diphosphate (ADP) previously found only in platelets. Because these results suggested that the P2T receptor may be an early marker for megakaryocytic differentiation, we studied whether this calcium- signaling receptor is also expressed in Dami cells, a human megakaryocytic leukemia cell line. Here we report evidence that Dami cells express a P2T receptor for ADP. The calcium response EC50 values for ADP, 2-methylthioadenosine diphosphate (2-MeS-ADP), and adenosine 5′-O-(2-thiodiphosphate) (ADP beta S) in Dami cells are 0.4 mumol/L, 0.04 mumol/L, and 2 mumol/L, respectively, which approximate the potencies of these agonists in K562 cells and in platelets. The platelet P2T receptor antagonists 2-methylthioadenosine triphosphate (2- MeS-ATP), and 2-chloroadenosine triphosphate (2-Cl-ATP) were surprisingly potent agonists at the P2T receptor in both Dami and K562 cells. Dami cells, unlike K562 cells and platelets, also respond to adenosine triphosphate (ATP) and uridine triphosphate (UTP) with an increase in intracellular calcium. Adenosine monophosphate (AMP) is an effective antagonist of the response to ADP, 2-MeS-ADP, ADP beta S, 2- MeS-ATP, and 2-Cl-ATP, but not to ATP and UTP. The responses to maximal concentrations of UTP in combination with either ADP, 2-MeS-ADP, ADP beta S, or 2-MeS-ATP are additive. In contrast, ADP in combination with either 2-MeS-ADP, ADP beta S, 2-MeS-ATP, or 2-Cl-ATP are not additive. UTP desensitized Dami cells to ATP but not to ADP, 2-MeS-ADP, ADP beta S, or 2-MeS-ATP. Addition of ATP after UTP desensitization antagonized subsequent responsiveness to ADP. The data suggest that the receptor for ADP may be a unique P2T subtype, and the receptor for ATP and UTP is distinct from that of ADP and is most characteristic of the P2U (nucleotide) receptor subtype. Activation of either the P2T or P2U receptor causes a rapid generation of inositol trisphosphate in Dami cells.
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Murgo, AJ, JG Contrera, and FD Sistare. "Evidence for separate calcium-signaling P2T and P2U purinoceptors in human megakaryocytic Dami cells." Blood 83, no. 5 (March 1, 1994): 1258–67. http://dx.doi.org/10.1182/blood.v83.5.1258.bloodjournal8351258.
Full textAbstract:
Recently (J Pharmacol Exp Ther 261:580, 1992), we have shown that K562 leukemia cells express a calcium-signaling purinoceptor with characteristics of the P2T receptor subtype for adenosine diphosphate (ADP) previously found only in platelets. Because these results suggested that the P2T receptor may be an early marker for megakaryocytic differentiation, we studied whether this calcium- signaling receptor is also expressed in Dami cells, a human megakaryocytic leukemia cell line. Here we report evidence that Dami cells express a P2T receptor for ADP. The calcium response EC50 values for ADP, 2-methylthioadenosine diphosphate (2-MeS-ADP), and adenosine 5′-O-(2-thiodiphosphate) (ADP beta S) in Dami cells are 0.4 mumol/L, 0.04 mumol/L, and 2 mumol/L, respectively, which approximate the potencies of these agonists in K562 cells and in platelets. The platelet P2T receptor antagonists 2-methylthioadenosine triphosphate (2- MeS-ATP), and 2-chloroadenosine triphosphate (2-Cl-ATP) were surprisingly potent agonists at the P2T receptor in both Dami and K562 cells. Dami cells, unlike K562 cells and platelets, also respond to adenosine triphosphate (ATP) and uridine triphosphate (UTP) with an increase in intracellular calcium. Adenosine monophosphate (AMP) is an effective antagonist of the response to ADP, 2-MeS-ADP, ADP beta S, 2- MeS-ATP, and 2-Cl-ATP, but not to ATP and UTP. The responses to maximal concentrations of UTP in combination with either ADP, 2-MeS-ADP, ADP beta S, or 2-MeS-ATP are additive. In contrast, ADP in combination with either 2-MeS-ADP, ADP beta S, 2-MeS-ATP, or 2-Cl-ATP are not additive. UTP desensitized Dami cells to ATP but not to ADP, 2-MeS-ADP, ADP beta S, or 2-MeS-ATP. Addition of ATP after UTP desensitization antagonized subsequent responsiveness to ADP. The data suggest that the receptor for ADP may be a unique P2T subtype, and the receptor for ATP and UTP is distinct from that of ADP and is most characteristic of the P2U (nucleotide) receptor subtype. Activation of either the P2T or P2U receptor causes a rapid generation of inositol trisphosphate in Dami cells.
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Mo, M., S. G. Eskin, and W. P. Schilling. "Flow-induced changes in Ca2+ signaling of vascular endothelial cells: effect of shear stress and ATP." American Journal of Physiology-Heart and Circulatory Physiology 260, no. 5 (May 1, 1991): H1698—H1707. http://dx.doi.org/10.1152/ajpheart.1991.260.5.h1698.
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The effect of hemodynamic flow on apparent cytosolic free Ca2+ concentration ([Ca2+]i) of cultured bovine aortic endothelial cells was examined in the absence and presence of adenine nucleotides using microfluorimetric analysis of fura-2 fluorescence. In the absence of adenine nucleotides, flow-induced shear stress produced little change (less than 10 nM) in [Ca2+]i. Similar results were obtained using calf pulmonary artery and human umbilical vein endothelial cells. However, addition of the adenine nucleotides ATP, ADP, or AMP under flow conditions produced a transient peak increase in [Ca2+]i that was followed by a sustained elevation. The rank order of potency for the peak response was ADP greater than or equal to ATP much much greater than AMP. Adenosine was without effect on [Ca2+]i. Washout of ATP resulted in the immediate return of [Ca2+]i to basal values, indicating that the effect of ATP was rapidly reversible. Decreasing the flow rate to zero during the sustained phase also resulted in an immediate decrease of [Ca2+]i. Similar results were obtained with ADP and AMP but not with the nonhydrolyzable adenine nucleotide analogues alpha,beta-methyleneadenosine-5'-diphosphate, beta,gamma-imidoadenosine-5'-triphosphate, or beta,gamma-methyleneadenosine-5'-triphosphate. Furthermore, the rate of [Ca2+]i decrease upon cessation of flow during the sustained phase of the response to ATP was inversely proportional to the ATP concentration. These results suggest that hydrolysis of ATP to adenosine by the ectonucleotidase is responsible for the termination of the ATP response under zero-flow conditions. Evaluation of the dose- and flow-dependent response of the cells to ATP indicates that convective-diffusive transport of ATP may play an important role in regulation of endothelial cell [Ca2+]i in presence of ectonucleotidase activity and could have important consequences for the regulation of blood flow in the vasculature.
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Konduri, Girija G., Ivane Bakhutashvili, Recia Frenn, Indira Chandrasekhar, Elizabeth R. Jacobs, and Ashwani K. Khanna. "P2Y purine receptor responses and expression in the pulmonary circulation of juvenile rabbits." American Journal of Physiology-Heart and Circulatory Physiology 287, no. 1 (July 2004): H157—H164. http://dx.doi.org/10.1152/ajpheart.00617.2003.
Full textAbstract:
The purine nucleotide ATP mediates pulmonary vasodilation at birth by stimulation of P2Y purine receptors in the pulmonary circulation. The specific P2Y receptors in the pulmonary circulation and the segmental distribution of their responses remain unknown. We investigated the effects of purine nucleotides, ATP, ADP, and AMP, and pyrimidine nucleotides, UTP, UDP, and UMP, in juvenile rabbit pulmonary arteries for functional characterization of P2Y receptors. We also studied the expression of P2Y receptor subtypes in pulmonary arteries and the role of nitric oxide (NO), prostaglandins, and cytochrome P-450 metabolites in the response to ATP. In conduit size arteries, ATP, ADP, and AMP caused greater relaxation responses than UTP, UDP, and UMP. In resistance vessels, ATP and UTP caused comparable vasodilation. The response to ATP was attenuated by the P2Y antagonist cibacron blue, the NO synthase antagonist Nω-nitro-l-arginine methyl ester (l-NAME), and the cytochrome P-450 inhibitor 17-octadecynoic acid but not by the P2X antagonist α,β-methylene ATP or the cyclooxygenase inhibitor indomethacin in conduit arteries. In the resistance vessels, l-NAME caused a more complete inhibition of the responses to ATP and UTP. Responses to AMP and UMP were NO and endothelium dependent, whereas responses to ADP and UDP were NO and endothelium independent in the conduit arteries. RT-PCR showed expression of P2Y1, P2Y2, and P2Y4 receptors, but not P2Y6 receptors, in lung parenchyma, pulmonary arteries, and pulmonary artery endothelial cells. These data suggest that distinct P2Y receptors mediate the vasodilator responses to purine and pyrimidine nucleotides in the juvenile rabbit pulmonary circulation. ATP appears to cause NO-mediated vasodilation predominantly through P2Y2 receptors on endothelium.
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Guo, Jinli, Guanyu Zhu, Lianguo Li, Huan Liu, and Shuang Liang. "Ultraweak photon emission in strawberry fruit during ripening and aging is related to energy level." Open Life Sciences 12, no. 1 (November 13, 2017): 393–98. http://dx.doi.org/10.1515/biol-2017-0046.
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AbstractBackgroundUltra-weak photon emission (UPE), or biophoton emission, is a phenomenon observed in various living organisms, including plants. In this study, we analyzed the UPE from ripening strawberry fruits, to elucidate its source and association with cellular energy.MethodsFreshly harvested and stored strawberry fruits were measured for levels of UPE and energy molecules adenosine triphosphate (ATP), adenosine monophosphate (AMP) and adenosine diphosphate (ADP). The associations between them were calculated.ResultsIn ripening fruit, a decrease in UPE positively correlated with declining levels of ATP, AMP, and energy charge. In harvested fruits, levels of UPE, ATP, and energy charge declined, but ADP and AMP increased.ConclusionChanges in UPE levels synchronized with changes in ATP and energy charge, which reflect cellular energy levels. Thus, cellular energy may be related to UPE, and may be an energy source for UPE.
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Green, A. K., P. H. Cobbold, and C. J. Dixon. "Elevated intracellular cyclic AMP exerts different modulatory effects on cytosolic free Ca2+ oscillations induced by ADP and ATP in single rat hepatocytes." Biochemical Journal 302, no. 3 (September 15, 1994): 949–55. http://dx.doi.org/10.1042/bj3020949.
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Single aequorin-injected hepatocytes respond to agonists acting via the phosphoinositide signalling pathway by the generation of oscillations in cytosolic free Ca2+ concentration ([Ca2+]free). The duration of [Ca2+]free transients is characteristic of the stimulating agonist. We have previously reported that ADP and ATP, which are believed to act through a single P(2y)-purinoceptor species, induce very different oscillatory [Ca2+]free responses in the majority of hepatocytes. We have interpreted these data as evidence for two separate Ca(2+)-mobilizing purinoceptors for these nucleotides. We show here that the elevation of intracellular cyclic AMP concentration, by the co-application of either dibutyryl cyclic AMP or 7 beta-desacetyl-7 beta-[gamma-(N-methylpiperazino)butyryl]- forskolin (L858051), exerts different modulatory effects on [Ca2+]free oscillations induced by ADP and ATP in single rat hepatocytes. Elevated intracellular cyclic AMP levels enhance the frequency and peak [Ca2+]free of transients induced by ADP. In contrast, the elevation of intracellular cyclic AMP levels in hepatocytes producing [Ca2+]free oscillations in response to ATP stimulates either an increase in the duration of transients or a sustained rise in [Ca2+]free. The data illustrate a further difference between the oscillatory [Ca2+]free responses of hepatocytes to ADP and ATP, thus further arguing against ADP and ATP acting via a single purinoceptor species.
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Blier, P. U., and H. E. Guderley. "MITOCHONDRIAL ACTIVITY IN RAINBOW TROUT RED MUSCLE: THE EFFECT OF TEMPERATURE ON THE ADP-DEPENDENCE OF ATP SYNTHESIS." Journal of Experimental Biology 176, no. 1 (March 1, 1993): 145–58. http://dx.doi.org/10.1242/jeb.176.1.145.
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By coupling mitochondrial ATP production to an enzymatic NADPH-producing reaction, we monitored the rates of ATP production spectrophotometrically. ATP production was coupled to the oxidation of malate and pyruvate. Interference by adenylate kinase was eliminated by using P1,P5- di(adenosine-5′)pentaphosphate and we found no interference by NADPH oxidase. We studied the kinetics of ATP synthesis by mitochondria from rainbow trout red muscle at three temperatures (8, 15 and 22 °C) and under two pH regimes (a constant pH of 7.4 and temperature-dependent pH). The mitochondria oxidized pyruvate and malate. The apparent Michaelis constant (Km,app) for ADP as well as the maximal velocity (Vmax) for ADP phosphorylation are markedly affected by temperature but not by pH. The Km,app for ADP decreases with increasing temperature while the Vmax increases. These data suggest that reduced temperatures decrease mitochondrial sensitivity to control by ADP availability.