Relevant bibliographies by topics / Enzymatic regulations

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Academic literature on the topic 'Enzymatic regulations'

Author: Grafiati
Published: 28 June 2023

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Journal articles on the topic "Enzymatic regulations"

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Xu, Chiwei, Brian Franklin, Hong-Wen Tang, Yannik Regimbald-Dumas, Yanhui Hu, Justine Ramos, Justin A. Bosch, Christians Villalta, Xi He, and Norbert Perrimon. "An in vivo RNAi screen uncovers the role of AdoR signaling and adenosine deaminase in controlling intestinal stem cell activity." Proceedings of the National Academy of Sciences 117, no. 1 (December 18, 2019): 464–71. http://dx.doi.org/10.1073/pnas.1900103117.

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Metabolites are increasingly appreciated for their roles as signaling molecules. To dissect the roles of metabolites, it is essential to understand their signaling pathways and their enzymatic regulations. From an RNA interference (RNAi) screen for regulators of intestinal stem cell (ISC) activity in theDrosophilamidgut, we identifiedadenosine receptor(AdoR) as a top candidate gene required for ISC proliferation. We demonstrate that Ras/MAPK and Protein Kinase A (PKA) signaling act downstream of AdoR and that Ras/MAPK mediates the major effect of AdoR on ISC proliferation. Extracellular adenosine, the ligand for AdoR, is a small metabolite that can be released by various cell types and degraded in the extracellular space by secreted adenosine deaminase. Interestingly, down-regulation ofadenosine deaminase-related growth factor A(Adgf-A) from enterocytes is necessary for extracellular adenosine to activate AdoR and induce ISC overproliferation. AsAdgf-Aexpression and its enzymatic activity decrease following tissue damage, our study provides important insights into how the enzymatic regulation of extracellular adenosine levels under tissue-damage conditions facilitates ISC proliferation.
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Noree, Chalongrat, and Naraporn Sirinonthanawech. "Coupled regulations of enzymatic activity and structure formation of aldehyde dehydrogenase Ald4p." Biology Open 9, no. 4 (April 15, 2020): bio051110. http://dx.doi.org/10.1242/bio.051110.

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Naka, Takashi. "The partition representation of enzymatic reaction networks and its application for searching bi-stable reaction systems." PLOS ONE 17, no. 1 (January 26, 2022): e0263111. http://dx.doi.org/10.1371/journal.pone.0263111.

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The signal transduction system, which is known as a regulatory mechanism for biochemical reaction systems in the cell, has been the subject of intensive research in recent years, and its design methods have become necessary from the viewpoint of synthetic biology. We proposed the partition representation of enzymatic reaction networks consisting of post-translational modification reactions such as phosphorylation, which is an important basic component of signal transduction systems, and attempted to find enzymatic reaction networks with bistability to demonstrate the effectiveness of the proposed representation method. The partition modifiers can be naturally introduced into the partition representation of enzymatic reaction networks when applied to search. By randomly applying the partition modifiers as appropriate, we searched for bistable and resettable enzymatic reaction networks consisting of four post-translational modification reactions. The proposed search algorithm worked well and we were able to find various bistable enzymatic reaction networks, including a typical bistable enzymatic reaction network with positive auto-feedbacks and mutually negative regulations. Since the search algorithm is divided into an evaluation function specific to the characteristics of the enzymatic reaction network to be searched and an independent algorithm part, it may be applied to search for dynamic properties such as biochemical adaptation, the ability to reset the biochemical state after responding to a stimulus, by replacing the evaluation function with one for other characteristics.
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Novoselov, M. A., I. I. Iline, Z. Sinovcic, and C. B. Phillips. "Is this imported food compliant with biosecurity regulations." New Zealand Plant Protection 67 (January 8, 2014): 322. http://dx.doi.org/10.30843/nzpp.2014.67.5761.

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Imported food products can carry biosecurity hazards such as animal plant and human diseases To reduce this risk imported foods that contain ingredients of animal origin must be retorted in compliance with a New Zealand Ministry for Primary Industries (MPI) Import Health Standard AgResearch and MPI have developed a proofofconcept enzymatic colorimetric assay (Iline et al 2013; Proof of concept for a biochemical test that differentiates between heattreated and nonheattreated food products New Zealand Plant Protection 66 3439) In April 2014 MPI asked for a test to determine if a tinned food imported from India had been retorted to standard Using the proofofconcept assay all 10 samples showed weak enzyme activity while control samples heated to the MPI standard produced no enzyme activity Normally the test detects activity of the enzyme glucose phosphate isomerase (GPI) but additional testing showed that GPI was inactive A possible source of the activity was a bacterial enzyme The results suggested the product had not been retorted to the MPI standard
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Sassone-Corsi, Paolo. "Minireview: NAD+, a Circadian Metabolite with an Epigenetic Twist." Endocrinology 153, no. 1 (January 1, 2012): 1–5. http://dx.doi.org/10.1210/en.2011-1535.

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Abstract A wide variety of endocrine, physiological, and metabolic functions follow daily oscillations. Most of these regulations are controlled at the level of gene expression by the circadian clock and, a remarkably coordinated transcription-translation machinery that exerts its function in virtually all mammalian cells. A large fraction of the genome is under control of the circadian clock, a regulation that is achieved through dynamic changes in chromatin states. Recent findings have demonstrated intimate connections between the circadian clock and epigenetic control. The case of nicotinamide adenine dinucleotide, which modulates the circadian activity of the deacetylase sirtuin 1, constitutes a paradigmatic example of the link between cyclic cellular metabolism and chromatin remodeling. Indeed, the clock transcriptional feedback loop is interlocked with the enzymatic loop of the nicotinamide adenine dinucleotide salvage pathway.
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Teparić, Renata, Mateja Lozančić, and Vladimir Mrša. "Evolutionary Overview of Molecular Interactions and Enzymatic Activities in the Yeast Cell Walls." International Journal of Molecular Sciences 21, no. 23 (November 26, 2020): 8996. http://dx.doi.org/10.3390/ijms21238996.

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Fungal cell walls are composed of a polysaccharide network that serves as a scaffold in which different glycoproteins are embedded. Investigation of fungal cell walls, besides simple identification and characterization of the main cell wall building blocks, covers the pathways and regulations of synthesis of each individual component of the wall and biochemical reactions by which they are cross-linked and remodeled in response to different growth phase and environmental signals. In this review, a survey of composition and organization of so far identified and characterized cell wall components of different yeast genera including Saccharomyces, Candida, Kluyveromyces, Yarrowia, and Schizosaccharomyces are presented with the focus on their cell wall proteomes.
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Gu, Bon-Hee, Myunghoo Kim, and Cheol-Heui Yun. "Regulation of Gastrointestinal Immunity by Metabolites." Nutrients 13, no. 1 (January 7, 2021): 167. http://dx.doi.org/10.3390/nu13010167.

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The gastrointestinal tract contains multiple types of immune cells that maintain the balance between tolerance and activation at the first line of host defense facing non-self antigens, including dietary antigens, commensal bacteria, and sometimes unexpected pathogens. The maintenance of homeostasis at the gastrointestinal tract requires stringent regulation of immune responses against various environmental conditions. Dietary components can be converted into gut metabolites with unique functional activities through host as well as microbial enzymatic activities. Accumulating evidence demonstrates that gastrointestinal metabolites have significant impacts on the regulation of intestinal immunity and are further integrated into the immune response of distal mucosal tissue. Metabolites, especially those derived from the microbiota, regulate immune cell functions in various ways, including the recognition and activation of cell surface receptors, the control of gene expression by epigenetic regulation, and the integration of cellular metabolism. These mucosal immune regulations are key to understanding the mechanisms underlying the development of gastrointestinal disorders. Here, we review recent advancements in our understanding of the role of gut metabolites in the regulation of gastrointestinal immunity, highlighting the cellular and molecular regulatory mechanisms by macronutrient-derived metabolites.
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Gu, Bon-Hee, Myunghoo Kim, and Cheol-Heui Yun. "Regulation of Gastrointestinal Immunity by Metabolites." Nutrients 13, no. 1 (January 7, 2021): 167. http://dx.doi.org/10.3390/nu13010167.

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The gastrointestinal tract contains multiple types of immune cells that maintain the balance between tolerance and activation at the first line of host defense facing non-self antigens, including dietary antigens, commensal bacteria, and sometimes unexpected pathogens. The maintenance of homeostasis at the gastrointestinal tract requires stringent regulation of immune responses against various environmental conditions. Dietary components can be converted into gut metabolites with unique functional activities through host as well as microbial enzymatic activities. Accumulating evidence demonstrates that gastrointestinal metabolites have significant impacts on the regulation of intestinal immunity and are further integrated into the immune response of distal mucosal tissue. Metabolites, especially those derived from the microbiota, regulate immune cell functions in various ways, including the recognition and activation of cell surface receptors, the control of gene expression by epigenetic regulation, and the integration of cellular metabolism. These mucosal immune regulations are key to understanding the mechanisms underlying the development of gastrointestinal disorders. Here, we review recent advancements in our understanding of the role of gut metabolites in the regulation of gastrointestinal immunity, highlighting the cellular and molecular regulatory mechanisms by macronutrient-derived metabolites.
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Medina-Herrera, Miriam del Rocío, María de la Luz Xochilt Negrete-Rodríguez, José Luis Álvarez-Trejo, Midory Samaniego-Hernández, Leopoldo González-Cruz, Aurea Bernardino-Nicanor, and Eloy Conde-Barajas. "Evaluation of Non-Conventional Biological and Molecular Parameters as Potential Indicators of Quality and Functionality of Urban Biosolids Used as Organic Amendments of Agricultural Soils." Applied Sciences 10, no. 2 (January 10, 2020): 517. http://dx.doi.org/10.3390/app10020517.

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Biosolids are waste from wastewater treatment and have a high content of organic matter and nutrients. In this study, not conventional physicochemical and biological properties of biosolids produced during different seasons of the year were evaluated. These properties are not considered in environmental regulations; however, they are of agronomic interest as indicators of quality and functionality in soils. Also, molecular analysis by Fourier-transform infrared (FTIR) was conducted, enzymatic analysis using the APIZYM® system was performed and two indices of functional and microbial diversity were established. The results showed that the biosolids had a high content of total organic carbon, total nitrogen, P, and K. FTIR analyses showed that chemical composition of biosolids was similar during all year. The C and N of microbial biomass demonstrated presence of active microorganisms, as well as a uniformity in its richness and abundance of species that could present a positive synergy with soil microorganisms. The enzymatic activities showed that the biosolids contained an enzymatic machinery available to promote the mineralisation of the organic matter of biosolids and could even transcend into the soil. Finally, biological properties can be used as indicators of quality and functionality of biosolids before being used as an organic amendment, especially in agricultural soils.
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Batool, Sadia, Hafiz Naeem Asghar, Muhammad Asif Shehzad, Sanaullah Yasin, Muhammad Sohaib, Fahim Nawaz, Gulzar Akhtar, Khuram Mubeen, Zahir Ahmad Zahir, and Muhammad Uzair. "Zinc-Solubilizing Bacteria-Mediated Enzymatic and Physiological Regulations Confer Zinc Biofortification in Chickpea (Cicer arietinum L.)." Journal of Soil Science and Plant Nutrition 21, no. 3 (June 28, 2021): 2456–71. http://dx.doi.org/10.1007/s42729-021-00537-6.

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Dissertations / Theses on the topic "Enzymatic regulations"

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Hull, Lynn. "Enzymatic Regulation of Opioid Antinociception and Tolerance." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1875.

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ENZYMATIC REGULATION OF OPIOID ANTINOCICEPTION AND TOLERANCE By Lynn C. Hull, Ph.D. A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University. Virginia Commonwealth University, 2009 Director: William L. Dewey, Ph.D. Department of Pharmacology and Toxicology The involvement of kinases in opioid actions has long been established. The acute actions of opioids, through the Gi/Go G-proteins, cause the inhibition of adenylyl cyclase and therefore a decrease in protein kinase A (PKA) activation. Additionally, acute opioid administration may cause the G-protein to activate the phospholipase C (PLC)-mediated cascade leading to the activation of protein kinase C (PKC). The phosphorylation of the MOR which can lead to both desensitization by uncoupling of the G-protein coupled receptors (GPCRs) from the G-proteins and to internalization by recruitment of β-arrestins has long been identified as a key process in tolerance. Phosphorylation by PKA and PKC leads primarily to uncoupling of the receptor from the G-proteins. Phosphorylation of the receptor by G-protein coupled receptor kinase (GRK) leads to the recruitment of β-arrestins and internalization of the receptor. Many in vitro studies have come to the conclusion that GRK induced internalization plays a more central role in the tolerance to high efficacy opioids and a lesser role in low- and moderate-efficacy opioid tolerance. In fact it has been hypothesized that morphine, a moderate-efficacy opioid, causes no internalization at all, while the desensitization of the receptor via phosphorylation by PKA and PKC plays a more central role in low- and moderate-efficacy opioid tolerance. We sought to test these in vitro findings in an in vivo model of opioid tolerance. Animals were made tolerant to one of a number of opioids of varying efficacy (low-efficacy meperidine, moderate-efficacy morphine and fentanyl, and high-efficacy [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO)) over an 8 hour period and then were administered one of the kinases’ inhibitors. Tolerance reversal was determined by challenging these mice with the same opioids to which they were tolerant. Calcium is known to play an important role in the acute antinociceptive actions of opioids as well as in opioid tolerance. Therefore it is important to determine how opioids are affecting the regulation of intracellular calcium. Our laboratory has previously shown that Calcium Induced Calcium Release (CICR), the ryanodine receptor and intracellular microsomal Ca2+ pools all play a role in opioids’ actions. It is also well known that mammalian ADP-ribosyl cyclase, CD38’s, product cADPR acts on the ryanodine receptor to cause Ca2+ release into the intracellular space. We chemically and genetically altered CD38 and then tested the acute effect of morphine as well as what effect these treatments had on morphine tolerance to determine what role if any, that CD38 may play in the acute actions of morphine antinociception as well as in morphine tolerance. Together, studies focusing on the role of an ADP-ribosyl cyclase, CD38, and 3 separate kinases, PKA, PKC and GRK, in opioids’ actions were performed in order to better understand the roles of these enzymes’ pathways in the actions of opioid-induced antinociception and subsequent development of tolerance. It is hoped that the results herein add useful knowledge to the general understanding of this drug class, and will one day be of use in the development of future analgesics and in the clinical treatment of pain and reduction in tolerance.
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Butler, Phillip Louis. "Enzymatic regulation of phosphatidylcholine synthesis via protein ubiquitination." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/473.

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Pulmonary surfactant is a critical surface-active substance consisting of dipalmitoylphosphatidylcholine (DPPtdCho) and key apoproteins that are produced and secreted into the airspace from alveolar type II epithelial cells. Deficiency of the surfactant leads to severe lung atelectasis, ventilatory impairment, and gas-exchange abnormalities. The generation of DPPtdCho in cells occurs via two integral routes: the de novo and remodeling pathways. The interplay between these pathways has not been investigated. Overexpression of the remodeling enzyme, acyl-CoA:lysophosphatidylcholine acyltransferase (LPCAT1), in epithelia decreases de novo PtdCho synthesis without significantly altering cellular phospholipid mass; this occurs through increased degradation of cholinephosphotransferase (CPT1), the terminal enzyme of the de novo pathway. CPT1 is degraded by multi-ubuiquitination and trafficking via the lysosomal pathway. When expressed in lung epithelia, CPT1 mutants harboring arginine substitutions at multiple carboxyl-terminal lysine residues exhibited proteolytic resistance to effects of LPCAT1 overexpression. Cellular expression of these CPT1 mutants also restores de novo PtdCho synthesis to levels normally observed in lung epithelia. Further studies demonstrate that the SCF (Skip-Cullen-F-box) ubiquitin E3 ligase component, β-TrCP, was sufficient to degrade CPT1. Similar to CPT1, LPCAT1 levels are also regulated at the level of protein stability. However, LPCAT1 is a polyubiquitinated enzyme processed within the proteasome. Similar to CPT1, β-TrCP is the putative E3 ubiquitin ligase subunit responsible for LPCAT1 ubiquitination. β-TrCP appears to dock and ubiquitinate LPCAT1 within its amino-terminus. Collectively, these observations indicate the presence of cross-talk between the phospholipid remodeling and de novo pathways; this involves tight regulation by site-specific ubiquitination of indispensable regulatory enzymes catalyzed by SCF ubiquitin E3 ligase members that mechanistically provide homeostatic control of cellular phospholipid content.
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Yang, Zhimou. "Molecular hydrogels : design, synthesis, enzymatic regulation, and biological applications /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202006%20YANG.

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Chen, Beibei. "Novel mechanisms for enzymatic regulation of phosphatidylcholine synthesis by proteolysis." Diss., University of Iowa, 2008. https://ir.uiowa.edu/etd/199.

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Pulmonary surfactant is a critical surface-active substance consisting of dipalmitoylphosphatidylcholine (DPPtdCho) and key apoproteins that are produced and secreted into the airspace from alveolar type II epithelial cells. Surfactant deficiency leads to severe lung atelectasis, ventilatory impairment, and gas-exchange abnormalities. These are features of the acute lung injury syndrome, characterized by a strong pro-inflammatory component where cytokines or bacteria infections greatly impair surfactant DPPtdCho biosynthesis. The key enzyme needed to produce surfactant DPPtdCho is a rate-limiting enzyme CTP: phosphocholine cytidylyltransferase (CCTalpha). Calmodulin (CaM), rather than disruption of an NH2-terminal PEST sequence, stabilizes CCTalpha from actions of the proteinase, calpain. Mapping and site-directed mutagenesis of CCTalpha uncovered a motif (LQERVDKVK) harboring a vital recognition site, Q243, whereby CaM directly binds to the enzyme. Mutagenesis of CCTalpha Q243 not only resulted in loss of CaM binding, but also led to complete calpain resistance in vitro and in vivo. These data suggest that CaM, by antagonizing calpain, serves as a novel binding partner for CCTalpha that stabilizes the enzyme under pro-inflammatory stress. We further show that CCTalpha does not undergo polyubiquitination and proteasomal degradation. Rather, the enzyme is monoubiquitinated at a molecular site (K57) juxtaposed near its NLS resulting in disruption of its interaction with importin, nuclear exclusion, and subsequent degradation within the lysosome. Importantly, by using CCTalpha-ubiquitin hybrid constructs that vary in the intermolecular distance between ubiquitin and the NLS, we show that CCTalpha monoubiquitination masks its NLS resulting in cytoplasmic retention. These results unravel a unique molecular mechanism whereby monoubiquitination governs the trafficking of a critical regulatory enzyme in vivo. Last, we identify FBXL2 as a novel F-box E3 ubiquitin ligase that targets CCTalpha for degradation. Interestingly, FBXL2 also interacts with CaM, and CaM directly disrupts CCTalpha and FBXL2 interaction. This study demonstrates in the first time that adenoviral gene transfer of CaM attenuates the deleterious effects of P. aeruginosa infection by improving several parameters of pulmonary mechanics in animal models of sepsis-induced acute pulmonary injury. Collectively, these studies reveal a novel regulatory mechanism for phosphatidylcholine synthesis that may provide important clues to understanding the pathobiology of acute lung injury.
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Chen, Yiyuan. "Regulation studies on human pyruvate kinases." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33175.

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Human pyruvate kinase performs the last step in glucose glycolysis in all cells and organisms and can be a key regulator of glycolytic flux. Pyruvate produced by PYK is transported into the mitochondria to fuel the TCA cycle, which enables the production of ATP; the main energy source of the cell. Human PYK contains four isoforms: M1 (found in muscle, heart and brain), M2 (in foetal cells and tumours), L (liver), and R (red blood cells) PYK. M2PYK plays a crucial role in tumour cell proliferation; by down-regulating metabolic flux, upstream metabolites can be used for protein and DNA synthesis. Reprogramming the metabolism of fast proliferating cells is called the 'Warburg effect'. The biological relevance of the different isoform activities is also discussed. For example RPYK in red blood cells is exposed to slowly altering metabolite concentrations, especially after intestinal absorption in plasma and RBCs uptake some of the metabolites. This thesis describes biochemical and biophysical studies of human M1PYK, M2PYK, LPYK, and RPYK. PYK is allosterically regulated by a range of metabolites. A comparative enzyme kinetics study of the four isoforms was performed to examine the mechanisms of activation and inhibition of these small molecule regulators, including all 20 amino acids and the thyroid hormone T3. The redox state of the environment was also found to be an important regulator of PYK activity. All four PYK isoforms were successfully expressed and purified. Interestingly, only M2PYK and RPYK were strongly regulated by amino acids and metabolites. We also found that the redox state regulates the activity of all four PYK isoforms as well as the sensitivity of M2PYK in response to natural regulators. These studies also confirmed the dissociation of tetrameric PYK into inactive monomers as an important mechanism of regulation, particularly for M2PYK activity. Nuclear magnetic resonance (NMR) and Small-angle X-ray scattering (SAXS) studies were performed to investigate the conformational behaviour of PYK isoforms in solution and to compare the effects of ligand binding. NMR data of all four isoforms reveal a conserved binding mechanism between isoforms and specific amino acids. SAXS data of all four isoforms demonstrate that ligands affect tetramerisation of PYK isoforms.
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Marković, Marija [Verfasser]. "Regulation and enzymatic properties of renal cytochrome P450 isoforms / Marija Markovic." Berlin : Freie Universität Berlin, 2009. http://d-nb.info/1023708906/34.

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Muise, Aleixo Michael (Aleixo Michael L. ). Carleton University Dissertation Chemistry. "Enzymatic regulation of glycerol metabolism in the overwintering gall moth Epiblema Scudderiana." Ottawa, 1993.

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Copp, Steven Wesley. "Enzymatic regulation of skeletal muscle oxygen transport: novel roles for neuronal nitric oxide synthase." Diss., Kansas State University, 2013. http://hdl.handle.net/2097/15512.

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Doctor of Philosophy
Department of Anatomy and Physiology
Timothy I. Musch
Nitric oxide (NO) is synthesized via distinct NO synthase (NOS) enzymes and constitutes an essential cardiovascular signaling molecule. Whereas important vasomotor contributions of endothelial NOS (eNOS) have been well-described, the specific vasomotor contributions of nNOS-derived NO in healthy subjects during exercise are unknown. The purpose of this dissertation is to test the global hypothesis that nNOS-derived NO is a critical regulator of exercising skeletal muscle vascular control. Specifically, we utilized the selective nNOS inhibitor S-methyl-L-thiocitrulline (SMTC) to investigate the effects of nNOS-derived NO on skeletal muscle vascular function within established rodent models of exercise performance. The first investigation (Chapter 2) identifies that nNOS inhibition with SMTC increases mean arterial pressure (MAP) and reduces rat hindlimb skeletal muscle blood flow at rest whereas there are no effects during low-speed (20 m/min) treadmill running. In Chapter 3 it is reported that nNOS inhibition with SMTC reduces blood flow during high-speed treadmill running (>50 m/min) with the greatest relative effects found in highly glycolytic fast-twitch muscles and muscle parts. Chapter 4 demonstrates that nNOS-derived NO modulates contracting skeletal muscle blood flow (increases), O2 consumption (VO2, increases), and force production (decreases) in the rat spinotrapezius muscle and thus impacts the microvascular O2 delivery-VO2 ratio (which sets the microvascular partial pressure of O2, PO2mv, and represents the pressure head that drives capillary-myocyte O2 diffusion). In Chapter 5 we report that systemic administration of the selective nNOS inhibitor SMTC does not impact lumbar sympathetic nerve discharge. This reveals that the SMTC-induced peripheral vascular effects described herein reflect peripheral nNOS-derived NO signaling as opposed to centrally-derived regulation. In conclusion, nNOS-derived NO exerts exercise-intensity and muscle fiber-type selective peripheral vascular effects during whole-body locomotor exercise. In addition, nNOS-derived NO modulates skeletal muscle contractile and metabolic function and, therefore, impacts the skeletal muscle PO2mv. These data identify novel integrated roles for nNOS-derived NO within healthy skeletal muscle and have important implications for populations associated with reduced NO bioavailability and/or impaired nNOS structure and/or function specifically (e.g., muscular dystrophy, chronic heart failure, advanced age, etc.).
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Lundqvist, Johan. "Enzymatic Regulation of Steroidogenesis and Nuclear Receptor Activation : Special Focus on Vitamin D and Sex Hormones." Doctoral thesis, Uppsala universitet, Institutionen för farmaceutisk biovetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-151740.

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Enzyme-catalyzed reactions are important to regulate steroidogenesis and nuclear receptor activation. The present investigation examines the role of steroid metabolism catalyzed by CYP7B1 for regulation of hormone receptor activation and the effects of vitamin D on enzymatic regulation of steroidogenesis. The study reports data indicating that CYP7B1 can regulate estrogenic signaling by converting estrogens into inactive or less active metabolites. Similar results were obtained for CYP7B1-mediated metabolism of some androgen receptor ligands, indicating that CYP7B1 can be involved also in the regulation of androgenic signaling. CYP7B1 substrates and metabolites were found to exert androgenic effects in a cell line-specific manner. Furthermore, cell line differences were observed in the expression pattern for androgen receptor comodulators. This thesis reports that 1α,25-dihydroxyvitamin D3 alters the gene expression and enzyme activity of CYP21A2 and CYP17A1 leading to suppressed production of aldosterone, dehydroepiandrosterone and androstenedione in adrenocortical cells. These are novel findings on vitamin D action. A mechanism is reported for the vitamin D-mediated regulation of the CYP21A2 gene. Data indicate that vitamin D receptor interacting repressor (VDIR) and Williams syndrome transcription factor (WSTF) are key comodulators in this novel vitamin D receptor (VDR)-mediated mechanism. Furthermore, the results indicate that altered expression levels of VDIR and WSTF can shift the suppressing effect of vitamin D to a stimulatory effect. Also, epigenetic components were found to be involved in the effects of vitamin D on CYP21A2 transcriptional rate. In addition, a functional vitamin D response element was identified in the CYP21A2 promoter. This study also reports that 1α,25-dihydroxyvitamin D3 affects sex hormone production in a tissue-specific way. Gene expression and enzyme activity of aromatase were found to be downregulated in cells derived from breast, but not in cells derived from prostate and adrenal cortex. The production of estradiol and dihydrotestosterone was altered in a tissue-selective manner following vitamin D treatment. These findings are of importance for the discussion on vitamin D as a potential anti-breast cancer agent.
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Cousin, Charlotte. "La gestion des sources carbonées chez Bacillus subtilis - Stratégie de validation expérimentale guidée par le modèle mathématique." Electronic Thesis or Diss., Paris, AgroParisTech, 2014. http://www.theses.fr/2014AGPT0008.

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Dans ce travail, nous avons établi un modèle dynamique d’équations différentielles de la glycolyse de Bacillus subtilis, comprenant à la fois les régulations transcriptionnelles et enzymatiques. La validation complète d’un modèle aussi complexe n’est pas faisable à l’heure actuelle. De ce fait, nous avons développé une stratégie de validation, guidée par le modèle, pour diminuer le nombre d’expériences et pour se focaliser uniquement sur les points clés de la régulation. L’analyse du modèle à l’équilibre a donc fait ressortir : les propriétés structurelles fortes de la glycolyse, les enzymes clés impliqués et les régulations enzymatiques indispensables. Notre objectif était donc de valider les régulations enzymatiques prédites et de démontrer les propriétés structurelles du modèle d’un point de vue biologique en les perturbant. Premièrement, le modèle prédit un certain nombre de régulations enzymatiques critiques que nous avons vérifié expérimentalement. Notre approche, guidée par le modèle mathématique, nous a permis de faire des découvertes inattendues. Le modèle prédit que la glucose-6-phosphate déshydrogénase et la phosphofructokinase sont inactivées par le phosphoenolpyruvate (PEP). Nous avons purifié les enzymes de B. subtilis et nous avons pu démontrer pour les deux enzymes une inhibition non compétitive par le PEP. Le modèle prédit également que la pyruvate kinase est activée par le ribose-5-phosphate (R5P). De manière inattendue, les essais enzymatiques avec la pyruvate kinase purifiée de B. subtilis et taguée en N-terminus n’a montré aucune activation par le R5P ou par aucun des activateurs connus de la pyruvate kinase chez d’autres espèces. En revanche, la pyruvate kinase purifiée de B.subtilis, mais taguée en C-terminus est bien activée par le R5P, démontrant ainsi l’implication de la partie N-terminale de la protéine dans la stabilité de l’enzyme. Enfin, le modèle a également démontré que la pyruvate kinase et la phosphofructokinase sont fortement corrélées afin de maintenir la robustesse de la glycolyse. Il est donc intéressant de constater que les gènes codant pour ces deux enzymes forment un opéron (pfk-pyk). Afin de perturber cette régulation, nous avons découplé les gènes de cet opéron, chacun sous contrôle d’un promoteur inductible. Les résultats montrent que la robustesse de la glycolyse de B. subtilis est très forte, et qu’elle est très difficile à perturber. Pour conclure, ce travail a permis de valider le modèle mathématique établi en amont, tout en démontrant les difficultés et les atouts d’une collaboration entre mathématiques et biologie, pour expliquer les réseaux biologiques aussi complexes
In this study, we established a dynamical differential equation model of glycolysis in Bacillus subtilis that couples enzymatic and transcriptional regulation. Full experimental validation of such a complex model is currently not feasible. Thus, we built a model-driven validation strategy to decrease the number of experiments and focus only on several key points of the regulation. Model analysis at steady-state pointed out: strong structural properties of glycolysis, key enzymes involved and enzymatic regulations that seem indispensable. Our objective was to validate the predicted enzymatic regulation, demonstrate the structural properties from a biological perspective and perturb them in order to validate the model. First, the model predicted critical enzymatic regulations that we verified experimentally. This in silico-driven approach led us to some unexpected discoveries. Glucose-6-phosphate dehydrogenase and phosphofructokinase were both predicted by the model to be inactivated by phosphoenolpyruvate (PEP). We purified the enzymes from B. subtilis and were able to demonstrate uncompetitive inhibition by PEP for both of them. Moreover, pyruvate kinase, catalyzing the last step of glycolysis, was predicted to be activated by ribose-5-phosphate (R5P). Enzymatic assays with N-terminally tagged B. subtilis pyruvate kinase showed no activation by R5P, or any known activator of pyruvate kinases from other species. By contrast, enzymatic assays with C-terminally tagged B. subtilis pyruvate kinase showed the predicted R5P activation, suggesting the implication of the N-terminus in B. subtilis pyruvate kinase stability. Finally, the model analysis showed that pyruvate kinase and phosphofructokinase need to be strongly correlated to maintain the robustness of glycolysis. This notion is supported by the fact that genes coding for these enzymes constitute an operon (pfk-pyk). In order to perturb the robust regulation of glycolysis, we constructed B. subtilis with the genes pfk and pyk uncoupled, each under control of a separate inducible promoter. The results show high-robustness of B. subtilis glycolysis that was difficult to perturb. In the end, the mathematical model has been validated. This work has demonstrated the shortcomings and the advantages of working at the interface between mathematics and biology, which is necessary for full understanding of high-complexity biological networks
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Books on the topic "Enzymatic regulations"

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Hatzios, Kriton K., ed. Regulation of Enzymatic Systems Detoxifying Xenobiotics in Plants. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-015-8927-7.

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K, Hatzios Kriton, North Atlantic Treaty Organization. Scientific Affairs Division., and NATO Advanced Research Workshop on Regulation of Enzymatic Systems Detoxifying Xenobiotics in Plants (1996 : Chalkidikē, Greece), eds. Regulation of enzymatic systems detoxifying xenobiotics in plants. Dordrecht: Kluwer Academic Publishers, 1997.

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Hatzios, Kriton K. Regulation of Enzymatic Systems Detoxifying Xenobiotics in Plants. Springer, 2010.

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Book chapters on the topic "Enzymatic regulations"

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le Maire, Marc, Raymond Chabaud, and Guy Hervé. "Enzymatic Catalysis and Regulation." In Laboratory Guide to Biochemistry, Enzymology, and Protein Physical Chemistry, 91–140. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-3820-2_5.

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Somero, George N., and Fred N. White. "Enzymatic consequences under alphastat regulation." In Acid-Base Regulation and Body Temperature, 55–80. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5004-7_4.

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Frieden, Carl, and Michael H. Penner. "Experimental Determination of Rate Constants in Enzymatic Reactions." In Enzyme Dynamics and Regulation, 268–74. New York, NY: Springer New York, 1988. http://dx.doi.org/10.1007/978-1-4612-3744-0_32.

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Maier, K. P. "Urea synthesis and its enzymatic regulation." In Trends in Hepatology, 129–35. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-4904-1_13.

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Incledon, Bev J., and J. Christopher Hall. "Enzymatic De-Esterification of Xenobiotics in Plants." In Regulation of Enzymatic Systems Detoxifying Xenobiotics in Plants, 67–82. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-015-8927-7_6.

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Hatzios, K. K. "Regulation of Xenobiotic Degrading Enzymes with Herbicide Safeners." In Regulation of Enzymatic Systems Detoxifying Xenobiotics in Plants, 275–88. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-015-8927-7_20.

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Hatzios, K. K. "Regulation of Enzymatic Systems Detoxifying Xenobiotics in Plants: A Brief Overview and Directions for Future Research." In Regulation of Enzymatic Systems Detoxifying Xenobiotics in Plants, 1–5. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-015-8927-7_1.

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Link, G., K. Tiller, and S. Baginsky. "Glutathione, a Regulator of Chloroplast Transcription." In Regulation of Enzymatic Systems Detoxifying Xenobiotics in Plants, 125–37. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-015-8927-7_10.

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Cole, D. J., I. Cummins, P. J. Hatton, D. Dixon, and R. Edwards. "Glutathione Transferases in Crops and Major Weeds." In Regulation of Enzymatic Systems Detoxifying Xenobiotics in Plants, 139–54. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-015-8927-7_11.

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Irzyk, G. P., and E. P. Fuerst. "Characterization and Induction of Maize Glutathione S-Transferases Involved in Herbicide Detoxification." In Regulation of Enzymatic Systems Detoxifying Xenobiotics in Plants, 155–70. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-015-8927-7_12.

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Conference papers on the topic "Enzymatic regulations"

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"The algorithm for finding potentially oscillating behavior in enzymatic systems." In Bioinformatics of Genome Regulation and Structure/ Systems Biology. institute of cytology and genetics siberian branch of the russian academy of science, Novosibirsk State University, 2020. http://dx.doi.org/10.18699/bgrs/sb-2020-108.

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Lugagne, Jean-Baptiste, Diego A. Oyarzun, and Guy-Bart V. Stan. "Stochastic simulation of enzymatic reactions under transcriptional feedback regulation." In 2013 European Control Conference (ECC). IEEE, 2013. http://dx.doi.org/10.23919/ecc.2013.6669756.

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LIU, L., W. SCHULTZ, and JW HASTINGS. "pH REGULATION OF LUCIFERASE ACTIVITY IN DINOFLAGELLATES INVOLVES A NOVEL ENZYMATIC MECHANISM." In Proceedings of the 13th International Symposium. WORLD SCIENTIFIC, 2005. http://dx.doi.org/10.1142/9789812702203_0004.

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Contag, Christopher H., Pamela R. Contag, Stanley D. Spilman, David K. Stevenson, and David A. Benaron. "Photonic Monitoring of Infectious Disease and Gene Regulation." In Biomedical Optical Spectroscopy and Diagnostics. Washington, D.C.: Optica Publishing Group, 2006. http://dx.doi.org/10.1364/bosd.1996.dr1.

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Optical analyses of biological processes in living animals are limited by a lack of unique optical properties among key molecules. To overcome this limitation we directly labeled biological events with bioluminescent proteins as reporter molecules. In these studies the expression of luciferase was linked to either a bacteria] pathogen or to an inducible viral promoter. Infection of mice and expression from the viral promoter were monitored noninvasively using the photons transmitted through tissues of living mice as an assay of enzymatic activity indicative of expression. The effects of an antibiotic on bacterial infection was assessed in real-time. The inducible nature of the viral promoter was demonstrated in the skin of transgenic mice containing the promoter-reporter construct. The use of bioluminescent reporters may permit spatial and temporal analyses of a wide variety of biological processes in living mammals.
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Hulme, Paul, Simon Chi, Dominic Young, John Matyas, and Neil A. Duncan. "Enzymatic Digestion Technique Influences Regulatory Volume Decrease of Isolated Bovine Chondrocytes." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32671.

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Cell volume regulation has been observed in almost all cell types examined to date. When cells are exposed to hypotonic solutions a quick increase in volume is followed by a more gradual return, termed regulatory volume decrease (RVD). The mechanism associated with RVD depends upon cell type and species, but in bovine chondrocytes the non-selective osmolyte channels are mainly responsible [1]. In a chondrocyte, volume control is critical for the maintenance of metabolism, and biosynthesis. Volume fluctuations can be due to changes in hydrostatic pressure, fluid flows, deformation, and extracellular matrix (ECM) hydration. Alterations in hydration can occur during static loading of articular cartilage or during the early stages of osteoarthritis [1], which have been correlated with changes in cellular metabolism. The swelling behaviour of chondrocytes, and the mechanism by which they sense and respond to changes in their physico-chemical environment, are not well understood [1]. To investigate the effects of osmotic environment on chondrocyte behaviour it is often beneficial to isolate cells from the ECM, which can be achieved by a variety of techniques. To investigate the effect of isolation technique on the swelling behaviour of bovine chondrocytes, two enzymatic digestion techniques were chosen for this study.
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Besar, Bediha, and Kristina Woods. "Picosecond time scale solvent fluctuations and enzymatic regulation in hen egg white lysozyme ligand reactions." In 2011 36th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2011). IEEE, 2011. http://dx.doi.org/10.1109/irmmw-thz.2011.6105252.

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Tamura, Jun-ichi, Akihiro Yamaguchi, and Junko Tanaka. "SYNTHESIS OF BETAGLYCAN-TYPE TETRAOSYL HEXAPEPTIDE: A POSSIBLE PRECURSOR REGULATING ENZYMATIC ELONGATION TOWARD HEPARIN." In XXIst International Carbohydrate Symposium 2002. TheScientificWorld Ltd, 2002. http://dx.doi.org/10.1100/tsw.2002.727.

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Sutter, Thomas M., Terry S. Creasy, Matthew B. Dickerson, and Ryan S. Justice. "Power Response of a Muscle Actuator Driven by a Regenerative, Enzymatic Pressurization Mechanism." In ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/smasis2013-3098.

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Inspired by the characteristics of biological muscles, rubber muscle actuators (RMAs) are lightweight and compliant structures that deliver high power/weight ratios and are currently under investigation for use in soft robotics, prosthetics, and specialized aircraft. RMA actuation is accomplished by inflating the structure’s air bladder, which results in the contraction of the muscle. In this proceedings paper, we describe the use of gaseous products from enzymatically-catalyzed reactions to pressurize and drive the motion of RMAs. Specifically, this paper details the power envelope of RMAs driven by the urease-catalyzed production of CO2, under dynamic loading conditions. The use of enzymatically catalyzed, gas-producing reactions is advantageous for powering RMAs, as these systems may be self-regulating and self-regenerating. Reaction design parameters for sizing the gas source to RMA power requirements and power envelope results are reported for gas-powered actuator dynamics tested on a linear motion test assembly. The power response to increasing loads reflects the partial pressure over the reaction slurry; therefore, the chemistry and reactor scale affect the entire structure’s efficiency. We outline the reactor space-time design constraints that facilitate a tailored power response for urease catalyzed gas generation sources.
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Khadka, Dipendra, Gi-Su Oh, Hyung-Jin Kim, SeungHoon Lee, Su-bin Lee, Subham Sharma, Seon Young Kim, et al. "Abstract 2717: Role of NAD+level by NQO1 enzymatic action in regulation of hair regrowth that prevents chemotherapy-induced alopecia." In Proceedings: AACR Annual Meeting 2019; March 29-April 3, 2019; Atlanta, GA. American Association for Cancer Research, 2019. http://dx.doi.org/10.1158/1538-7445.sabcs18-2717.

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Khadka, Dipendra, Gi-Su Oh, Hyung-Jin Kim, SeungHoon Lee, Su-bin Lee, Subham Sharma, Seon Young Kim, et al. "Abstract 2717: Role of NAD+level by NQO1 enzymatic action in regulation of hair regrowth that prevents chemotherapy-induced alopecia." In Proceedings: AACR Annual Meeting 2019; March 29-April 3, 2019; Atlanta, GA. American Association for Cancer Research, 2019. http://dx.doi.org/10.1158/1538-7445.am2019-2717.

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Reports on the topic "Enzymatic regulations"

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Zhang, Yimin, Arpit Bhatt, Garvin Heath, Mae Thomas, and Jason Renzaglia. Federal Air Pollutant Emission Regulations and Preliminary Estimates of Potential-to-Emit from Biorefineries. Pathway #1: Dilute-Acid and Enzymatic Deconstruction of Biomass-to-Sugars and Biological Conversion of Sugars-to-Hydrocarbons. Office of Scientific and Technical Information (OSTI), February 2016. http://dx.doi.org/10.2172/1239063.

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Granot, David, and Richard Amasino. Regulation of Senescence by Sugar Metabolism. United States Department of Agriculture, January 2003. http://dx.doi.org/10.32747/2003.7585189.bard.

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Research objectives a. Analyze transgenic plants that undergo rapid senescence due to increased expression of hexokinase. b. Determine if hexokinase-induced senescence accelerates natural senescence using senescence specific promoters that drive expression of a reporter gene (GUS) and a cytokinin producing gene (IPT - isopentyl transferase). c. Isolate and analyze plant genes that suppress sugar-induced cell death (SICD) in yeast, genes that potentially are involved in programmed cell death and senescence in plants. Background to the topic Leaf senescence is a regulated process of programmed cell death (PCD) in which metabolites are recycled to other active parts of the plant. Senescence associated genes (SAGs) are expressed throughout leaf senescence. Sugar flux and metabolism is thought to playa fundamental regulatory role in senescence. We found that transgenic tomato plants with high hexokinase activity, the initial enzymatic step of sugar (hexose) metabolism, undergo rapid leaf senescence, directly correlated with hexokinase activity. These plants provide a unique opportunity to analyze the regulatory role of sugar metabolism in senescence, and its relation to cytokinin, a senescence-inhibiting hormone. In addition, we found that sugar induces programmed cells death of yeast cells in direct correlation to hexokinase activity. We proposed to use the sugar induced cell death (SICD) to isolate Arabidopsis genes that suppress SICD. Such genes could potentially be involved in senescence induced PCD in plants. Major conclusions The promoters of Arabidopsis senescence-associated genes, SAG12 and SAGI3, are expressed in senescing tomato leaves similar to their expression in Arabidopsis leaves, indicating that these promoters are good senescence markers for tomato plants. Increased hexokinase activity accelerated senescence and induced expression of pSAG12 and pSAG13 promoters in tomato plants, suggesting that sugar regulate natural senescence via hexokinase. Expression of IPT, a cytokinin producing gene, under pSAG12 and pSAG13 promoters, delayed senescence of tomato leaves. Yet, senescence accelerated by hexokinase was epistatic over cytokinin, indicating that sugar regulation of senescence is dominant over the senescence-inhibiting hormone. A gene designated SFP1, which is similar to the major super family monosaccharide transporters, is induced during leaf senescence in Arabidopsis and may be involved in sugar transport during senescence. Accordingly, adult leaves accumulate sugars that may accelerate hexokinase activity. Light status of the entire plant affects the senescence of individual leaves. When individual leaves are darkened, senescence is induced in the covered leaves. However, whole adult plant placed in darkness show delayed senescence. In a search for Arabidopsis genes that suppress SICD we isolated 8 cDNA clones which confer partial resistance to SICD. One of the clones encodes a vesicle associated membrane protein - VAMP. This is the first evidence that vesicle trafficking might be involved in cell death. Implications Increased hexokinase activity accelerates senescence. We hypothesized that, reduced hexokinase activity may delay senescence. Preliminary experiments using a hexokinase inhibitor support this possible implication. Currently we are analyzing various practical approaches to delay leaf senescence via hexokinase inhibition. .
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Jander, Georg, and Daniel Chamovitz. Investigation of growth regulation by maize benzoxazinoid breakdown products. United States Department of Agriculture, January 2015. http://dx.doi.org/10.32747/2015.7600031.bard.

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Introduction Previous research had suggested that benzoxazinoids, a class of defensive metabolites found in maize, wheat, rye, and wild barley, are not only direct insect deterrents, but also influence other areas of plant metabolism. In particular, the benzoxazinoid 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxa- zin-3(4H)- one (DIMBOA) was implicated in: (i) altering plant growth by interfering with auxin signaling, and (ii) leading to the induction of gene expression changes and secondary plant defense responses. The overall goal of this proposal was to identify mechanisms by which benzoxazinoids influence other aspects of plant growth and defense. Specifically, the following hypotheses were proposed to be tested as part of an approved BARD proposal: Benzoxazinoid breakdown products directly interfere with auxin perception Global changes in maize and barley gene expression are induced by benzoxazinoid activation. There is natural variation in the maize photomorphogenic response to benzoxazinoids. Although the initial proposal included experiments with both maize and barley, there were some technical difficulties with the proposed transgenic barley experiments and most of the experimental results were generated with maize. Summary of major findings Previous research by other labs, involving both maize and other plant species, had suggested that DIMBOA alters plant growth by interfering with auxin signaling. However, experiments conducted in both the Chamovitz and the Jander labs using Arabidopsis and maize, respectively, were unable to confirm previously published reports of exogenously added DIMBOA effects on auxin signaling. Nevertheless, analysis of bx1 and bx2 maize mutant lines, which have almost no detectable benzoxazinoids, showed altered responses to blue light signaling. Transcriptomic analysis of maize mutant lines, variation in inbred lines, and responses to exogenously added DIMBOA showed alteration in the transcription of a blue light receptor, which is required for plant growth responses. This finding provides a novel mechanistic explanation of the trade-off between growth and defense that is often observed in plants. Experiments by the Jander lab and others had demonstrated that DIMBOA not only has direct toxicity against insect pests and microbial pathogens, but also induces the formation of callose in both maize and wheat. In the current project, non-targeted metabolomic assays of wildtype maize and mutants with defects in benzoxazinoid biosynthesis were used to identify unrelated metabolites that are regulated in a benzoxazinoid-dependent manner. Further investigation identified a subset of these DIMBOA-responsive compounds as catechol, as well as its glycosylated and acetylated derivatives. Analysis of co-expression data identified indole-3-glycerol phosphate synthase (IGPS) as a possible regulator of benzoxazinoid biosynthesis in maize. In the current project, enzymatic activity of three predicted maize IGPS genes was confirmed by heterologous expression. Transposon knockout mutations confirmed the function of the maize genes in benzoxazinoid biosynthesis. Sub-cellular localization studies showed that the three maize IGPS proteins are co-localized in the plastids, together with BX1 and BX2, two previously known enzymes of the benzoxazinoid biosynthesis pathway. Implications Benzoxazinoids are among the most abundant and effective defensive metabolites in maize, wheat, and rye. Although there is considerable with-in species variation in benzoxazinoid content, very little is known about the regulation of this variation and the specific effects on plant growth and defense. The results of this research provide further insight into the complex functions of maize benzoxazinoids, which are not only toxic to pests and pathogens, but also regulate plant growth and other defense responses. Knowledge gained through the current project will make it possible to engineer benzoxazinoid biosynthesis in a more targeted manner to produce pest-tolerant crops without negative effects on growth and yield.
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Olszewski, Neil, and David Weiss. Role of Serine/Threonine O-GlcNAc Modifications in Signaling Networks. United States Department of Agriculture, September 2010. http://dx.doi.org/10.32747/2010.7696544.bard.

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Significant evidence suggests that serine/threonine-O-linked N-acetyl glucosamine0-(GlcNAc) modifications play a central role in the regulation of plant signaling networks. Forexample, mutations in SPINDLY,) SPY (an O-GlcNAc transferase,) OGT (promote gibberellin GA) (signal transduction and inhibit cytokinin responses. In addition, mutating both Arabidopsis OGTsSEC (and SPY) causes embryo lethality. The long-term goal of this research is to elucidate the mechanism by which Arabidopsis OGTs regulate signaling networks. This project investigated the mechanisms of O-GlcNAc regulation of cytokinin and gibberellin signaling, identified additional processes regulated by this modification and investigated the regulation of SEC activity. Although SPY is a nucleocytoplasmic protein, its site of action and targets were unknown. Severalstudies suggested that SPY acted in the nucleus where it modified nuclear components such as the DELLA proteins. Using chimeric GFP-SPY fused to a nuclear-export signal or to a nuclear-import signal, we showed that cytosolic, but not nuclear SPY, regulated cytokinin and GA signaling. We also obtained evidence suggesting that GA and SPY affect cytokinin signaling via a DELLA-independent pathway. Although SEC and SPY were believed to have overlapping functions, the role of SEC in cytokinin and GA signaling was unclear. The role of SEC in cytokinin and GA responses was investigated by partially suppressing SPY expression in secplants using a synthetic Spymicro RNA miR(SPY). The possible contribution of SEC to the regulation of GA and cytokinin signaling wastest by determining the resistance of the miR spy secplants to the GA biosynthesis inhibitor paclobutrazol and to cytokinin. We found that the transgenic plants were resistant to paclobutrazol and to cytokinin, butonlyata level similar to spy. Moreover, expressing SEC under the 35S promoter in spy mutant did not complement the spy mutation. Therefore, we believe that SEC does not act with SPY to regulate GA or cytokinin responses. The cellular targets of Spy are largely unknown. We identified the transcription factor TCP15 in a two-hybrid screen for SPY-interacting proteins and showed that both TCP15 and its closely homolog TCP14 were O-GlcNAc modified by bacterially-produced SEC. The significance of the interaction between SPY and these TCPs was examined by over-expressing the minwild-type and spy-4plants. Overexpression of TCP14 or TCP15 in wild-type background produced phenotypes typical of plants with increased cytokinin and reduced GA signaling. TCP14 overexpression phenotypes were strongly suppressed in the spy background, suggesting that TCP14 and TCP15 affect cytokinin and GA signaling and that SPY activates them. In agreement with this hypothesis, we created a tcp14tcp15 double mutant and found that it has defects similar to spyplants. In animals, O-GlcNAc modification is proposed to regulate the activity of the nuclear pore. Therefore, after discovering that SEC modified a nucleoporinNUP) (that also interacts with SPY, we performed genetic experiments exploring the relationship between NUPs and SPY nupspy double mutants exhibited phenotypes consistent with SPY and NUPs functioning in common processes and nupseeds were resistant to GA biosynthesis inhibitors. All eukaryotic OGTs have a TPR domain. Deletion studies with bacterially-expressed SEC demonstrated SEC'sTPR domain inhibits SEC enzymatic activity. Since the TPR domain interacts with other proteins, we propose that regulatory proteins regulate OGT activity by binding and modulating the inhibitory activity of the TPR domain.
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