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Journal articles on the topic 'NAD-bound'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Kalinina, Sviatlana, Christian Freymueller, Nilanjon Naskar, Bjoern von Einem, Kirsten Reess, Ronald Sroka, and Angelika Rueck. "Bioenergetic Alterations of Metabolic Redox Coenzymes as NADH, FAD and FMN by Means of Fluorescence Lifetime Imaging Techniques." International Journal of Molecular Sciences 22, no. 11 (May 31, 2021): 5952. http://dx.doi.org/10.3390/ijms22115952.

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Metabolic FLIM (fluorescence lifetime imaging) is used to image bioenergetic status in cells and tissue. Whereas an attribution of the fluorescence lifetime of coenzymes as an indicator for cell metabolism is mainly accepted, it is debated whether this is valid for the redox state of cells. In this regard, an innovative algorithm using the lifetime characteristics of nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) and flavin adenine dinucleotide (FAD) to calculate the fluorescence lifetime induced redox ratio (FLIRR) has been reported so far. We extended the FLIRR approach and present new results, which includes FLIM data of the various enzymes, such as NAD(P)H, FAD, as well as flavin mononucleotide (FMN). Our algorithm uses a two-exponential fitting procedure for the NAD(P)H autofluorescence and a three-exponential fit of the flavin signal. By extending the FLIRR approach, we introduced FLIRR1 as protein-bound NAD(P)H related to protein-bound FAD, FLIRR2 as protein-bound NAD(P)H related to free (unbound) FAD and FLIRR3 as protein-bound NAD(P)H related to protein-bound FMN. We compared the significance of extended FLIRR to the metabolic index, defined as the ratio of protein-bound NAD(P)H to free NAD(P)H. The statistically significant difference for tumor and normal cells was found to be highest for FLIRR1.

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2

Kim, Yong Ju. "A cryoprotectant induces conformational change in glyceraldehyde-3-phosphate dehydrogenase." Acta Crystallographica Section F Structural Biology Communications 74, no. 5 (April 16, 2018): 277–82. http://dx.doi.org/10.1107/s2053230x18004557.

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Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a glycolytic enzyme, catalyses the conversion of D-glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate. While mammalian and yeast GAPDHs are multifunctional proteins that have additional functions beyond those involved in glycolysis, including reactions related to nuclear RNA transport, DNA replication/repair, membrane fusion and cellular apoptosis, Escherichia coli GAPDH (ecGAPDH) has only been reported to function in glycolysis. The S-loop of GAPDH is required for interaction with its cofactor and with other proteins. In this study, the three-dimensional crystal structure of GAPDH treated with trehalose is reported at 2.0 Å resolution. Trehalose was used as a cryoprotectant for the GAPDH crystals. The structure of trehalose-bound ecGAPDH was compared with the structures of both NAD+-free and NAD+-bound ecGAPDH. At the S-loop, the bound trehalose in the GAPDH structure induces a 2.4° rotation compared with the NAD+-free ecGAPDH structure and a 3.1° rotation compared with the NAD+-bound ecGAPDH structure.

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3

Galloway, T. S., R. M. Tait, and S. van Heyningen. "Photolabelling of cholera toxin by NAD+." Biochemical Journal 242, no. 3 (March 15, 1987): 927–30. http://dx.doi.org/10.1042/bj2420927.

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When cholera toxin is incubated under u.v. light with NAD+ labelled in either the adenine or the nicotinamide moiety, radioactivity becomes covalently bound to the protein. The reaction is specific for cholera toxin, and is inhibited by excess unlabelled NAD+ or NAD analogues. Only the active A 1 chain of the toxin is labelled. The u.v.-absorption spectrum of the product is very similar to that of NAD+, and shows the same reaction with cyanide. The nature of the product is therefore different from that found when diphtheria toxin is photolabelled [Carroll & Collier (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 3307-3311] in that the yield is lower, but both moieties of the NAD molecule become bound.

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4

Bell, Charles E., Todd O. Yeates, and David Eisenberg. "Unusual conformation of nicotinamide adenine dinucleotide (NAD) bound to diphtheria toxin: A comparison with NAD bound to the oxidoreductase enzymes." Protein Science 6, no. 10 (December 31, 2008): 2084–96. http://dx.doi.org/10.1002/pro.5560061004.

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5

Aguilar-Arnal, Lorena, Suman Ranjit, Chiara Stringari, Ricardo Orozco-Solis, Enrico Gratton, and Paolo Sassone-Corsi. "Spatial dynamics of SIRT1 and the subnuclear distribution of NADH species." Proceedings of the National Academy of Sciences 113, no. 45 (October 24, 2016): 12715–20. http://dx.doi.org/10.1073/pnas.1609227113.

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Sirtuin 1 (SIRT1) is an NAD+-dependent deacetylase that functions as metabolic sensor of cellular energy and modulates biochemical pathways in the adaptation to changes in the environment. SIRT1 substrates include histones and proteins related to enhancement of mitochondrial function as well as antioxidant protection. Fluctuations in intracellular NAD+ levels regulate SIRT1 activity, but how SIRT1 enzymatic activity impacts on NAD+ levels and its intracellular distribution remains unclear. Here, we show that SIRT1 determines the nuclear organization of protein-bound NADH. Using multiphoton microscopy in live cells, we show that free and bound NADH are compartmentalized inside of the nucleus, and its subnuclear distribution depends on SIRT1. Importantly, SIRT6, a chromatin-bound deacetylase of the same class, does not influence NADH nuclear localization. In addition, using fluorescence fluctuation spectroscopy in single living cells, we reveal that NAD+ metabolism in the nucleus is linked to subnuclear dynamics of active SIRT1. These results reveal a connection between NAD+ metabolism, NADH distribution, and SIRT1 activity in the nucleus of live cells and pave the way to decipher links between nuclear organization and metabolism.

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6

Hu, Yumei, Weidong Liu, Satish R. Malwal, Yingying Zheng, Xinxin Feng, Tzu-Ping Ko, Chun-Chi Chen, et al. "Structures of Iridoid Synthase fromCantharanthus roseuswith Bound NAD+, NADPH, or NAD+/10-Oxogeranial: Reaction Mechanisms." Angewandte Chemie 127, no. 51 (November 13, 2015): 15698–702. http://dx.doi.org/10.1002/ange.201508310.

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7

Hu, Yumei, Weidong Liu, Satish R. Malwal, Yingying Zheng, Xinxin Feng, Tzu-Ping Ko, Chun-Chi Chen, et al. "Structures of Iridoid Synthase fromCantharanthus roseuswith Bound NAD+, NADPH, or NAD+/10-Oxogeranial: Reaction Mechanisms." Angewandte Chemie International Edition 54, no. 51 (November 13, 2015): 15478–82. http://dx.doi.org/10.1002/anie.201508310.

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8

Cummings, M. D., T. N. Hart, B. Hazes, and R. J. Read. "Modeling the structure of NAD bound to pertussis toxin." Acta Crystallographica Section A Foundations of Crystallography 52, a1 (August 8, 1996): C88. http://dx.doi.org/10.1107/s0108767396095566.

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9

Thomas, Leonard M., Angelica R. Harper, Whitney A. Miner, Helen O. Ajufo, Katie M. Branscum, Lydia Kao, and Paul A. Sims. "Structure ofEscherichia coliAdhP (ethanol-inducible dehydrogenase) with bound NAD." Acta Crystallographica Section F Structural Biology and Crystallization Communications 69, no. 7 (June 27, 2013): 730–32. http://dx.doi.org/10.1107/s1744309113015170.

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10

Niesner, R., P. Narang, H. Spiecker, V. Andresen, K. H. Gericke, and M. Gunzer. "Selective Detection of NADPH Oxidase in Polymorphonuclear Cells by Means of NAD(P)H-Based Fluorescence Lifetime Imaging." Journal of Biophysics 2008 (November 16, 2008): 1–13. http://dx.doi.org/10.1155/2008/602639.

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NADPH oxidase (NOX2) is a multisubunit membrane-bound enzyme complex that, upon assembly in activated cells, catalyses the reduction of free oxygen to its superoxide anion, which further leads to reactive oxygen species (ROS) that are toxic to invading pathogens, for example, the fungus Aspergillus fumigatus. Polymorphonuclear cells (PMNs) employ both nonoxidative and oxidative mechanisms to clear this fungus from the lung. The oxidative mechanisms mainly depend on the proper assembly and function of NOX2. We identified for the first time the NAD(P)H-dependent enzymes involved in such oxidative mechanisms by means of biexponential NAD(P)H-fluorescence lifetime imaging (FLIM). A specific fluorescence lifetime of 3670±140 picoseconds as compared to 1870 picoseconds for NAD(P)H bound to mitochondrial enzymes could be associated with NADPH bound to oxidative enzymes in activated PMNs. Due to its predominance in PMNs and due to the use of selective activators and inhibitors, we strongly believe that this specific lifetime mainly originates from NOX2. Our experiments also revealed the high site specificity of the NOX2 assembly and, thus, of the ROS production as well as the dynamic nature of these phenomena. On the example of NADPH oxidase, we demonstrate the potential of NAD(P)H-based FLIM in selectively investigating enzymes during their cellular function.

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11

Anderlund, Mikael, Torben L. Nissen, Jens Nielsen, John Villadsen, Jan Rydström, Bärbel Hahn-Hägerdal, and Morten C. Kielland-Brandt. "Expression of the Escherichia coli pntA andpntB Genes, Encoding Nicotinamide Nucleotide Transhydrogenase, in Saccharomyces cerevisiae and Its Effect on Product Formation during Anaerobic Glucose Fermentation." Applied and Environmental Microbiology 65, no. 6 (June 1, 1999): 2333–40. http://dx.doi.org/10.1128/aem.65.6.2333-2340.1999.

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ABSTRACT We studied the physiological effect of the interconversion between the NAD(H) and NADP(H) coenzyme systems in recombinantSaccharomyces cerevisiae expressing the membrane-bound transhydrogenase from Escherichia coli. Our objective was to determine if the membrane-bound transhydrogenase could work in reoxidation of NADH to NAD+ in S. cerevisiaeand thereby reduce glycerol formation during anaerobic fermentation. Membranes isolated from the recombinant strains exhibited reduction of 3-acetylpyridine-NAD+ by NADPH and by NADH in the presence of NADP+, which demonstrated that an active enzyme was present. Unlike the situation in E. coli, however, most of the transhydrogenase activity was not present in the yeast plasma membrane; rather, the enzyme appeared to remain localized in the membrane of the endoplasmic reticulum. During anaerobic glucose fermentation we observed an increase in the formation of 2-oxoglutarate, glycerol, and acetic acid in a strain expressing a high level of transhydrogenase, which indicated that increased NADPH consumption and NADH production occurred. The intracellular concentrations of NADH, NAD+, NADPH, and NADP+were measured in cells expressing transhydrogenase. The reduction of the NADPH pool indicated that the transhydrogenase transferred reducing equivalents from NADPH to NAD+.

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12

Moller, I. M., and W. Lin. "Membrane-Bound NAD(P)H Dehydrogenases in Higher Plant Cells." Annual Review of Plant Physiology 37, no. 1 (June 1986): 309–34. http://dx.doi.org/10.1146/annurev.pp.37.060186.001521.

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13

Joannou, C. L., and P. R. Brown. "NAD-dependent glutamate dehydrogenase fromPseudomonas aeruginosais a membrane-bound enzyme." FEMS Microbiology Letters 90, no. 2 (January 1992): 205–10. http://dx.doi.org/10.1111/j.1574-6968.1992.tb05153.x.

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14

Tsai, C. Stan, and D. J. Senior. "Dual coenzyme activities of high-Km aldehyde dehydrogenase from rat liver mitochondria." Biochemistry and Cell Biology 68, no. 4 (April 1, 1990): 751–57. http://dx.doi.org/10.1139/o90-108.

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Various kinetic approaches were carried out to investigate kinetic attributes for the dual coenzyme activities of mitochondrial aldehyde dehydrogenase from rat liver. The enzyme catalyses NAD+- and NADP+-dependent oxidations of ethanal by an ordered bi-bi mechanism with NAD(P)+ as the first reactant bound and NAD(P)H as the last product released. The two coenzymes presumably interact with the kinetically identical site. NAD+ forms the dynamic binary complex with the enzyme, while the enzyme-NAD(P)H complex formation is associated with conformation change(s). A stopped-flow burst of NAD(P)H formation, followed by a slower steady-state turnover, suggests that either the deacylation or the release of NAD(P)H is rate limiting. Although NADP+ is reduced by a faster burst rate, NAD+ is slightly favored as the coenzyme by virtue of its marginally faster turnover rate.Key words: aldehyde dehydrogenase, coenzyme preference.

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15

Okai, Masahiko, Norio Kudo, Woo Cheol Lee, Masayuki Kamo, Koji Nagata, and Masaru Tanokura. "Crystal Structures of the Short-Chain Flavin Reductase HpaC fromSulfolobus tokodaiiStrain 7 in Its Three States: NAD(P)+-Free, NAD+-Bound, and NADP+-Bound†,‡." Biochemistry 45, no. 16 (April 2006): 5103–10. http://dx.doi.org/10.1021/bi052313i.

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16

Zhang, Chunxiang, Jian Yang, Jonathan D. Jacobs, and Lisa K. Jennings. "Interaction of myeloperoxidase with vascular NAD(P)H oxidase-derived reactive oxygen species in vasculature: implications for vascular diseases." American Journal of Physiology-Heart and Circulatory Physiology 285, no. 6 (December 2003): H2563—H2572. http://dx.doi.org/10.1152/ajpheart.00435.2003.

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Vascular NAD(P)H oxidase-derived reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) have emerged as important molecules in the pathogenesis of atherosclerosis, hypertension, and diabetic vascular complications. Additionally, myeloperoxidase (MPO), a transcytosable heme protein that is derived from leukocytes, is also believed to play important roles in the above-mentioned inflammatory vascular diseases. Previous studies have shown that MPO-induced vascular injury responses are H2O2 dependent. It is well known that MPO can use leukocyte-derived H2O2; however, it is unknown whether the vascular-bound MPO can use vascular nonleukocyte oxidase-derived H2O2 to induce vascular injury. In the present study, ANG II was used to stimulate vascular NAD(P)H oxidases and increase their H2O2 production in the vascular wall, and vascular dysfunction was used as the vascular injury parameter. We demonstrated that vascular-bound MPO has sustained activity in the vasculature. MPO could use the vascular NAD(P)H oxidase-derived H2O2 to produce hypochlorus acid (HOCl) and its chlorinating species. More importantly, MPO derived HOCl and chlorinating species amplified the H2O2-induced vascular injury by additional impairment of endothelium-dependent relaxation. HOCl-modified low-density lipoprotein protein (LDL), a specific biomarker for the MPO-HOCl-chlorinating species pathway, was expressed in LDL and MPO-bound vessels with vascular NAD(P)H oxidase-derived H2O2. MPO-vascular NAD(P)H oxidase-HOCl-chlorinating species may represent a common pathogenic pathway in vascular diseases and a new mechanism involved in exacerbation of vascular diseases under inflammatory conditions.

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17

Franza, Thierry, Annika Rogstam, Saravanamuthu Thiyagarajan, Matthew J. Sullivan, Aurelie Derré-Bobillot, Mikael C. Bauer, Kelvin G. K. Goh, et al. "NAD+ pool depletion as a signal for the Rex regulon involved in Streptococcus agalactiae virulence." PLOS Pathogens 17, no. 8 (August 9, 2021): e1009791. http://dx.doi.org/10.1371/journal.ppat.1009791.

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In many Gram-positive bacteria, the redox-sensing transcriptional repressor Rex controls central carbon and energy metabolism by sensing the intra cellular balance between the reduced and oxidized forms of nicotinamide adenine dinucleotide; the NADH/NAD+ ratio. Here, we report high-resolution crystal structures and characterization of a Rex ortholog (Gbs1167) in the opportunistic pathogen, Streptococcus agalactiae, also known as group B streptococcus (GBS). We present structures of Rex bound to NAD+ and to a DNA operator which are the first structures of a Rex-family member from a pathogenic bacterium. The structures reveal the molecular basis of DNA binding and the conformation alterations between the free NAD+ complex and DNA-bound form of Rex. Transcriptomic analysis revealed that GBS Rex controls not only central metabolism, but also expression of the monocistronic rex gene as well as virulence gene expression. Rex enhances GBS virulence after disseminated infection in mice. Mechanistically, NAD+ stabilizes Rex as a repressor in the absence of NADH. However, GBS Rex is unique compared to Rex regulators previously characterized because of its sensing mechanism: we show that it primarily responds to NAD+ levels (or growth rate) rather than to the NADH/NAD+ ratio. These results indicate that Rex plays a key role in GBS pathogenicity by modulating virulence factor gene expression and carbon metabolism to harvest nutrients from the host.

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18

Penfound, Thomas, and John W. Foster. "NAD-Dependent DNA-Binding Activity of the Bifunctional NadR Regulator of Salmonella typhimurium." Journal of Bacteriology 181, no. 2 (January 15, 1999): 648–55. http://dx.doi.org/10.1128/jb.181.2.648-655.1999.

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ABSTRACT NadR is a 45-kDa bifunctional regulator protein. In vivo genetic studies indicate that NadR represses three genes involved in the biosynthesis of NAD. It also participates with an integral membrane protein (PnuC) in the import of nicotinamide mononucleotide, an NAD precursor. NadR was overexpressed and purified as a His-tagged fusion in order to study its DNA-binding properties. The protein bound to DNA fragments containing NAD box consensus sequences. NAD proved to be the relevant in vivo corepressor, but full NAD dependence of repressor activity required nucleotide triphosphates. DNA footprint analysis and gel shift assays suggest that NadR binds as a multimer to adjacent NAD boxes. The DNA-repressor complex would sequester a potential RNA polymerase binding site and thereby decrease expression of thenad regulon.

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19

Kishimoto, Toshihiko, Masaaki Itami, Tetsuya Yomo, Itaru Urabe, Yasuhiro Yamada, and Hirosuke Okada. "Improved methods for the preparation of N6-(2-carboxyethyl)-NAD and poly(ethylene glycol)-bound NAD(H)." Journal of Fermentation and Bioengineering 71, no. 6 (January 1991): 447–49. http://dx.doi.org/10.1016/0922-338x(91)90262-f.

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20

Vanhommerig, Sylvia A. M., Lamoraal A. Æ. Sluyterman, and Emmo M. Meijer. "Kinetic and modelling studies of NAD+ and poly(ethylene glycol)-bound NAD+ in horse liver alcohol dehydrogenase." Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology 1295, no. 2 (July 1996): 125–38. http://dx.doi.org/10.1016/0167-4838(96)00026-x.

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21

Gallais, Stéphane, Marie-Anne Pou de Crescenzo, and Danielle L. Laval-Martin. "Changes in soluble and membrane-bound isoforms of calcium-calmodulin-dependent and -independent NAD+ kinase, during the culture of after-ripened and dormant seeds of Avena sativa." Functional Plant Biology 27, no. 7 (2000): 649. http://dx.doi.org/10.1071/pp00010.

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Activities of the soluble and membrane-boundisoforms of Ca 2+ calmodulin (CaCam)-dependent and-independent NAD + kinases, were followed in theembryos during the culture of dormant (D) and after-ripened (AR) seeds ofAvena sativa L. Embryos of D and AR seeds differ mainly in the evolution ofmembrane-bound activities, the majority of which are CaCam-dependent andlinked to mitochondria. The in vivo application ofgibberellic acid, CaCl2 andH2O2, which enhanced germination,induced an enhancement of all CaCam-dependent isoforms. Trifluoperazine (TFP),a calmodulin antagonist, greatly enhanced all CaCam-dependent isoforms andabolished the differences between the NAD + kinaseactivities of the two kinds of embryo. In addition, TFP rendered embryosunable to resume axis growth, probably due to pleiotropic effects. In contrastto H2O2, the reducing agentdithiothreitol diminished the soluble CaCam-dependent enzyme and blocked thegermination of both types of seed, whereas it increased the dependentmembrane-bound activities. The results demonstrate (1) that theCaCam-dependent NAD + kinase isoforms —amongst which is the isoform bound to mitochondrial membranes — play animportant role at the end of sensu stricto germinationand during the following growth of Avena sativa; and (2)that an excess of activity of these isoforms could be markers of stress orlethal conditions.

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22

Chen, Meirong, Zuoqi Gai, Chiaki Okada, Yuxin Ye, Jian Yu, and Min Yao. "Flexible NAD+ Binding in Deoxyhypusine Synthase Reflects the Dynamic Hypusine Modification of Translation Factor IF5A." International Journal of Molecular Sciences 21, no. 15 (July 31, 2020): 5509. http://dx.doi.org/10.3390/ijms21155509.

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The eukaryotic and archaeal translation factor IF5A requires a post-translational hypusine modification, which is catalyzed by deoxyhypusine synthase (DHS) at a single lysine residue of IF5A with NAD+ and spermidine as cofactors, followed by hydroxylation to form hypusine. While human DHS catalyzed reactions have been well characterized, the mechanism of the hypusination of archaeal IF5A by DHS is not clear. Here we report a DHS structure from Pyrococcus horikoshii OT3 (PhoDHS) at 2.2 Å resolution. The structure reveals two states in a single functional unit (tetramer): two NAD+-bound monomers with the NAD+ and spermidine binding sites observed in multi-conformations (closed and open), and two NAD+-free monomers. The dynamic loop region V288–P299, in the vicinity of the active site, adopts different positions in the closed and open conformations and is disordered when NAD+ is absent. Combined with NAD+ binding analysis, it is clear that PhoDHS can exist in three states: apo, PhoDHS-2 equiv NAD+, and PhoDHS-4 equiv NAD+, which are affected by the NAD+ concentration. Our results demonstrate the dynamic structure of PhoDHS at the NAD+ and spermidine binding site, with conformational changes that may be the response to the local NAD+ concentration, and thus fine-tune the regulation of the translation process via the hypusine modification of IF5A.

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23

Jacobi, Tobias, and Christoph Woenckhaus. "NAD covalent-bound to dehydrogenases — a model compound for enzyme electrodes." Fresenius' Zeitschrift für analytische Chemie 324, no. 3-4 (January 1986): 274. http://dx.doi.org/10.1007/bf00487919.

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24

Chen, Yong-Qing, Jeroen van Beek, Hua Deng, John Burgner, and Robert Callender. "Vibrational Structure of NAD(P) Cofactors Bound to Three NAD(P) Dependent Enzymes: an Investigation of Ground State Activation." Journal of Physical Chemistry B 106, no. 41 (October 2002): 10733–40. http://dx.doi.org/10.1021/jp025635u.

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25

Kirby, Christina A., Atwood Cheung, Aleem Fazal, Michael D. Shultz, and Travis Stams. "Structure of human tankyrase 1 in complex with small-molecule inhibitors PJ34 and XAV939." Acta Crystallographica Section F Structural Biology and Crystallization Communications 68, no. 2 (January 21, 2012): 115–18. http://dx.doi.org/10.1107/s1744309111051219.

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The crystal structures of tankyrase 1 (TNKS1) in complex with two small-molecule inhibitors, PJ34 and XAV939, both at 2.0 Å resolution, are reported. The structure of TNKS1 in complex with PJ34 reveals two molecules of PJ34 bound in the NAD+donor pocket. One molecule is in the nicotinamide portion of the pocket, as previously observed in other PARP structures, while the second molecule is bound in the adenosine portion of the pocket. Additionally, unlike the unliganded crystallization system, the TNKS1–PJ34 crystallization system has the NAD+donor site accessible to bulk solvent in the crystal, which allows displacement soaking. The TNKS1–PJ34 crystallization system was used to determine the structure of TNKS1 in complex with XAV939. These structures provide a basis for the start of a structure-based drug-design campaign for TNKS1.

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26

Steuber, Julia, Walter Krebs, Michael Bott, and Peter Dimroth. "A Membrane-Bound NAD(P)+-Reducing Hydrogenase Provides Reduced Pyridine Nucleotides during Citrate Fermentation by Klebsiella pneumoniae." Journal of Bacteriology 181, no. 1 (January 1, 1999): 241–45. http://dx.doi.org/10.1128/jb.181.1.241-245.1999.

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ABSTRACT During anaerobic growth of Klebsiella pneumoniae on citrate, 9.4 mmol of H2/mol of citrate (4-kPa partial pressure) was formed at the end of growth besides acetate, formate, and CO2. Upon addition of NiCl2 (36 μM) to the growth medium, hydrogen formation increased about 36% to 14.8 mmol/mol of citrate (6 kPa), and the cell yield increased about 15%. Cells that had been harvested and washed under anoxic conditions exhibited an H2-dependent formation of NAD(P)H in vivo. The reduction of internal NAD(P)+ was also achieved by the addition of formate. In crude extracts, the H2:NAD+oxidoreductase activity was 0.13 μmol min−1mg−1, and 76% of this activity was found in the washed membrane fraction. The highest specific activities of the membrane fraction were observed in 50 mM potassium phosphate, with 1.6 μmol of NADPH formed min−1 mg−1 at pH 7.0 and 1.7 μmol of NADH formed min−1 mg−1 at pH 9.5. In the presence of the protonophore carbonyl cyanidem-chlorophenylhydrazone and the Na+/H+ antiporter monensin, the H2-dependent reduction of NAD+ by membrane vesicles decreased only slightly (about 16%). The NADP+- or NAD+-reducing hydrogenases were solubilized from the membranes with the detergent lauryldimethylamine-N-oxide or Triton X-100. NAD(P)H formation with H2 as electron donor, therefore, does not depend on an energized state of the membrane. It is proposed that hydrogen which is formed by K. pneumoniaeduring citrate fermentation is recaptured by a novel membrane-bound, oxygen-sensitive H2:NAD(P)+ oxidoreductase that provides reducing equivalents for the synthesis of cell material.

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27

Nakamura, S., M. Koga, S. Kataoka, M. Oda, T. Ohkubo, and Y. Kobayashi. "Structures of NADH and NAD+bound 3α-hydroxysteroid dehydrogenase fromPseudomonassp. B-0831." Acta Crystallographica Section A Foundations of Crystallography 64, a1 (August 23, 2008): C267. http://dx.doi.org/10.1107/s0108767308091460.

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28

LIN, LI-SHENG, LI-NA LIU, HUI-FANG HUANG, YUAN-ZHONG CHEN, BU-HONG LI, and ZHENG HUANG. "CHARACTERIZING FLUORESCENCE LIFETIME OF NAD(P)H IN HUMAN LEUKEMIC MYELOID CELLS AND MONONUCLEAR CELLS." Journal of Innovative Optical Health Sciences 06, no. 04 (October 2013): 1350042. http://dx.doi.org/10.1142/s1793545813500429.

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The aim of this ex vivo study was to explore the potential of using the fluorescence lifetime of intracellular reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) as a label-free indicator to characterize the differences between human leukemic myeloid cells and normal mononuclear cells (MNC). The steady-state and time-resolved autofluorescence of two human leukemic myeloid cell lines (K562, HL60) and MNC were measured by a spectrofluorimeter. According to excitation–emission matrix (EEM) analysis, the optimal emission of NAD(P)H in these cells suspensions occurred at 445 nm. Furthermore, the fluorescence lifetimes of NAD(P)H in leukemic myeloid cells and MNC were determined by fitting the time-resolved autofluorescence data. The mean fluorescence lifetimes of NAD(P)H in K562, HL60, and MNC cells were 5.57 ± 1.19, 4.45 ± 0.71, and 7.31 ± 0.60 ns, respectively. There was a significant difference in the mean lifetime of NAD(P)H between leukemic myeloid cells and MNC (p < 0.05). The difference was essentially caused by the change in relative concentration of free and protein-bound NAD(P)H. This study suggests that the mean fluorescence lifetime of NAD(P)H might be a potential label-free indicator for differentiating leukemic myeloid cells from MNC.

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de Crescenzo, Marie-Anne Pou, Ken Goto, Isabelle A. Carré, and Danielle L. Laval-Martin. "Regulation of a NAD + Kinase Activity Isolated from Asynchronous Cultures of the Achlorophyllous ZC Mutant of Euglena gracilis." Zeitschrift für Naturforschung C 52, no. 9-10 (October 1, 1997): 623–35. http://dx.doi.org/10.1515/znc-1997-9-1009.

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NAD+ kinase was isolated by chromatography steps from asynchronous cultures of the achlorophyllous ZC mutant of Euglena gracilis. A non Ca2+-calmodulin dependent form, whose activity was stimulated by EGTA, was selected for its large quantity and high specific activity. Studies of the kinetic parameters revealed two kinds of NAD+ binding site, depending on NAD+ concentrations, and changes induced by EGTA, Ca2+ and Ca2+-calmodulin. The search for effectors, soluble (S) and membrane-bound (P), in Euglena gracilis synchronously grown (in a light-dark regime of 12h:12h), and collected at circadian times (CT) - corresponding to the maximum, CT 17, and to the trough, CT 09, of the circadian rhythm of NAD+ kinase activity - was also undertaken by testing the modulations of the kinetic parameters of the prepared NAD+ kinase. The results suggest: (i) structural changes of NAD+ binding sites depending on NAD+ concentrations; (ii) possible binding of the Mg-ATP-2 (or Ca-ATP-2) on the NAD+ sites, because of their common ADP motif; and (iii) different and specific modulations of the kinetic parameters of the two types of NAD+ binding site by the Ca2+-calmodulin complex. In addition, the results indicate, in pelletable fractions isolated at CT 09 and CT 17, the presence of two kinds of effector: (i) the first one, possibly Ca2+, which increases the Umax’s while decreasing the binding of NAD+; (ii) the second one, possibly the Ca2+-calmodulin complex, which provokes a complete reverse effect. Each of these two effectors seems to be, alternatively and rhythmically (eight circadian hours apart), partially released from the membranes

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30

Hu, Yumei, Weidong Liu, Satish R. Malwal, Yingying Zheng, Xinxin Feng, Tzu-Ping Ko, Chun-Chi Chen, et al. "Titelbild: Structures of Iridoid Synthase fromCantharanthus roseuswith Bound NAD+, NADPH, or NAD+/10-Oxogeranial: Reaction Mechanisms (Angew. Chem. 51/2015)." Angewandte Chemie 127, no. 51 (December 3, 2015): 15517. http://dx.doi.org/10.1002/ange.201510890.

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31

Unciuleac, Mihaela-Carmen, Yehuda Goldgur, and Stewart Shuman. "Two-metal versus one-metal mechanisms of lysine adenylylation by ATP-dependent and NAD+-dependent polynucleotide ligases." Proceedings of the National Academy of Sciences 114, no. 10 (February 21, 2017): 2592–97. http://dx.doi.org/10.1073/pnas.1619220114.

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Polynucleotide ligases comprise a ubiquitous superfamily of nucleic acid repair enzymes that join 3′-OH and 5′-PO4DNA or RNA ends. Ligases react with ATP or NAD+and a divalent cation cofactor to form a covalent enzyme-(lysine-Nζ)–adenylate intermediate. Here, we report crystal structures of the founding members of the ATP-dependent RNA ligase family (T4 RNA ligase 1; Rnl1) and the NAD+-dependent DNA ligase family (Escherichia coliLigA), captured as their respective Michaelis complexes, which illuminate distinctive catalytic mechanisms of the lysine adenylylation reaction. The 2.2-Å Rnl1•ATP•(Mg2+)2structure highlights a two-metal mechanism, whereby: a ligase-bound “catalytic” Mg2+(H2O)5coordination complex lowers the pKaof the lysine nucleophile and stabilizes the transition state of the ATP α phosphate; a second octahedral Mg2+coordination complex bridges the β and γ phosphates; and protein elements unique to Rnl1 engage the γ phosphate and associated metal complex and orient the pyrophosphate leaving group for in-line catalysis. By contrast, the 1.55-Å LigA•NAD+•Mg2+structure reveals a one-metal mechanism in which a ligase-bound Mg2+(H2O)5complex lowers the lysine pKaand engages the NAD+α phosphate, but the β phosphate and the nicotinamide nucleoside of the nicotinamide mononucleotide (NMN) leaving group are oriented solely via atomic interactions with protein elements that are unique to the LigA clade. The two-metal versus one-metal dichotomy demarcates a branchpoint in ligase evolution and favors LigA as an antibacterial drug target.

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Czygier, M., and S. A. Strumiło. "Basic properties of the pyruvate dehydrogenase complex isolated from aurochs heart." Acta Biochimica Polonica 41, no. 4 (December 31, 1994): 453–57. http://dx.doi.org/10.18388/abp.1994_4696.

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The purified aurochs (Bison bonasus, European bison) heart pyruvate dehydrogenase complex (PDC) has a set of subunits typical of mammalian PDC. PDC from aurochs heart contains firmly bound tiamine pyrophosphate in the amount providing over 50% of the maximal activity of the complex. The apparent value for activation energy of PDC is 60 kJ/mol. The Michaelis constant values for aurochs heart PDC are 22.4 +/- 1.0, 3.3 +/- 0.1 and 24.4 +/- 3.6 microM for pyruvate, CoA and NAD, accordingly. Acetyl-CoA is a competitive inhibitor with respect to CoA (Ki = 14.2 +/- 0.4 microM), whereas NADH gives the same inhibition with respect to NAD (Ki = 46.9 +/- 10.0 microM). The Km for CoA and NAD of the aurochs heart PDC are lower than that of domestic animals PDC.

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Kitson, T. M., and K. E. Kitson. "Probing the active site of cytoplasmic aldehyde dehydrogenase with a chromophoric reporter group." Biochemical Journal 300, no. 1 (May 15, 1994): 25–30. http://dx.doi.org/10.1042/bj3000025.

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3,4-Dihydro-3-methyl-6-nitro-2H-1,3-benzoxazin-2-one (‘DMNB’) reacts with cytoplasmic aldehyde dehydrogenase in a similar way to that previously observed with the structurally related p-nitrophenyl dimethylcarbamate, but provides a covalently linked p-nitrophenol-containing reporter group at the enzyme's active site. The pKa of the enzyme-linked reporter group is much higher than that of free p-nitrophenol, which is consistent with its being in a very hydrophobic environment, or possibly one containing negative charge. Upon binding of NAD+ to the modified enzyme, the pKa falls dramatically, by about 4 1/2 pH units. This implies that under these conditions there is a positive charge near the p-nitrophenoxide moiety, perhaps that of the nicotinamide ring of NAD+. The modified enzyme binds NAD+ very tightly; neither gel filtration nor dialysis is effective in separating them. However, the reporter group provides a convenient way of monitoring the displacement of this bound NAD+ when NADH is added.

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34

González, Javier M., Ricardo Marti-Arbona, Julian C. H. Chen, Brian Broom-Peltz, and Clifford J. Unkefer. "Conformational changes on substrate binding revealed by structures of Methylobacterium extorquens malate dehydrogenase." Acta Crystallographica Section F Structural Biology Communications 74, no. 10 (September 19, 2018): 610–16. http://dx.doi.org/10.1107/s2053230x18011809.

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Three high-resolution X-ray crystal structures of malate dehydrogenase (MDH; EC 1.1.1.37) from the methylotroph Methylobacterium extorquens AM1 are presented. By comparing the structures of apo MDH, a binary complex of MDH and NAD+, and a ternary complex of MDH and oxaloacetate with ADP-ribose occupying the pyridine nucleotide-binding site, conformational changes associated with the formation of the catalytic complex were characterized. While the substrate-binding site is accessible in the enzyme resting state or NAD+-bound forms, the substrate-bound form exhibits a closed conformation. This conformational change involves the transition of an α-helix to a 310-helix, which causes the adjacent loop to close the active site following coenzyme and substrate binding. In the ternary complex, His284 forms a hydrogen bond to the C2 carbonyl of oxaloacetate, placing it in a position to donate a proton in the formation of (2S)-malate.

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35

MONTAINE, France, Jean-Pierre LENDERS, and Robert R. CRICHTON. "Use of a polymer-bound flavin derivative for the rapid regeneration of NAD(P)+ from NAD(P)H in dehydrogenase systems." European Journal of Biochemistry 164, no. 2 (April 1987): 329–36. http://dx.doi.org/10.1111/j.1432-1033.1987.tb11062.x.

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36

Deng, Hua, John Burgner, and Robert Callender. "Raman spectroscopic studies of NAD coenzymes bound to malate dehydrogenases by difference techniques." Biochemistry 30, no. 36 (September 1991): 8804–11. http://dx.doi.org/10.1021/bi00100a011.

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37

Koide, S., S. Yokoyama, H. Matsuzawa, T. Miyazawa, and T. Ohta. "Conformation of NAD+ Bound to Allosteric L-Lactate Dehydrogenase Activated by Chemical Modification." Journal of Biological Chemistry 264, no. 15 (May 1989): 8676–79. http://dx.doi.org/10.1016/s0021-9258(18)81845-2.

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38

Jin, Xiangshu, and James H. Geiger. "Structures of NAD+- and NADH-bound 1-L-myo-inositol 1-phosphate synthase." Acta Crystallographica Section D Biological Crystallography 59, no. 7 (June 27, 2003): 1154–64. http://dx.doi.org/10.1107/s0907444903008205.

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39

Kato, Nobuo, Tomohide Yamagami, Masayuki Shimao, and Chikahiro Sakazawa. "Regeneration of NAD(H) covalently bound to formate dehydrogenase with several second enzymes." Applied Microbiology and Biotechnology 25, no. 5 (February 1987): 415–18. http://dx.doi.org/10.1007/bf00253310.

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40

Li, Mingguang, Brian J. Petteys, Julie M. McClure, Veena Valsakumar, Stefan Bekiranov, Elizabeth L. Frank, and Jeffrey S. Smith. "Thiamine Biosynthesis in Saccharomyces cerevisiae Is Regulated by the NAD+-Dependent Histone Deacetylase Hst1." Molecular and Cellular Biology 30, no. 13 (May 3, 2010): 3329–41. http://dx.doi.org/10.1128/mcb.01590-09.

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ABSTRACT Genes encoding thiamine biosynthesis enzymes in microorganisms are tightly regulated such that low environmental thiamine concentrations activate transcription and high concentrations are repressive. We have determined that multiple thiamine (THI) genes in Saccharomyces cerevisiae are also regulated by the intracellular NAD+ concentration via the NAD+-dependent histone deacetylase (HDAC) Hst1 and, to a lesser extent, Sir2. Both of these HDACs associate with a distal region of the affected THI gene promoters that does not overlap with a previously defined enhancer region bound by the thiamine-responsive Thi2/Thi3/Pdc2 transcriptional activators. The specificity of histone H3 and/or H4 deacetylation carried out by Hst1 and Sir2 at the distal promoter region depends on the THI gene being tested. Hst1/Sir2-mediated repression of the THI genes occurs at the level of basal expression, thus representing the first set of transcription factors shown to actively repress this gene class. Importantly, lowering the NAD+ concentration and inhibiting the Hst1/Sum1 HDAC complex elevated the intracellular thiamine concentration due to increased thiamine biosynthesis and transport, implicating NAD+ in the control of thiamine homeostasis.

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EGUCHI, Tamotsu, Takashi IIZUKA, Tadashi KAGOTANI, Joung Hee LEE, Itaru URABE, and Hirosuke OKADA. "Covalent linking of poly(ethyleneglycol)-bound NAD with Thermus thermophilus malate dehydrogenase. NAD(H)-regeneration unit for a coupled second-enzyme reaction." European Journal of Biochemistry 155, no. 2 (March 1986): 415–21. http://dx.doi.org/10.1111/j.1432-1033.1986.tb09507.x.

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42

Leben, Köhler, Radbruch, Hauser, and Niesner. "Systematic Enzyme Mapping of Cellular Metabolism by Phasor-Analyzed Label-Free NAD(P)H Fluorescence Lifetime Imaging." International Journal of Molecular Sciences 20, no. 22 (November 7, 2019): 5565. http://dx.doi.org/10.3390/ijms20225565.

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In the past years, cellular metabolism of the immune system experienced a revival, as it has become clear that it is not merely responsible for the cellular energy supply, but also impacts on many signaling pathways and, thus, on diverse cellular functions. Label-free fluorescence lifetime imaging of the ubiquitous coenzymes NADH and NADPH (NAD(P)H-FLIM) makes it possible to monitor cellular metabolism in living cells and tissues and has already been applied to study metabolic changes both under physiologic and pathologic conditions. However, due to the complex distribution of NAD(P)H-dependent enzymes in cells, whose distribution continuously changes over time, a thorough interpretation of NAD(P)H-FLIM results, in particular, resolving the contribution of various enzymes to the overall metabolic activity, remains challenging. We developed a systematic framework based on angle similarities of the phase vectors and their length to analyze NAD(P)H-FLIM data of cells and tissues based on a generally valid reference system of highly abundant NAD(P)H-dependent enzymes in cells. By using our analysis framework, we retrieve information not only about the overall metabolic activity, i.e., the fraction of free to enzyme-bound NAD(P)H, but also identified the enzymes predominantly active within the sample at a certain time point with subcellular resolution. We verified the performance of the approach by applying NAD(P)H-FLIM on a stromal-like cell line and identified a different group of enzymes that were active in the cell nuclei as compared to the cytoplasm. As the systematic phasor-based analysis framework of label-free NAD(P)H-FLIM can be applied both in vitro and in vivo, it retains the unique power to enable dynamic enzyme-based metabolic investigations, at subcellular resolution, in genuine environments.

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Choe, Hyunjun, Jung Min Ha, Jeong Chan Joo, Hyunook Kim, Hye-Jin Yoon, Seonghoon Kim, Sang Hyeon Son, et al. "Structural insights into the efficient CO2-reducing activity of an NAD-dependent formate dehydrogenase fromThiobacillussp. KNK65MA." Acta Crystallographica Section D Biological Crystallography 71, no. 2 (January 23, 2015): 313–23. http://dx.doi.org/10.1107/s1399004714025474.

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CO2fixation is thought to be one of the key factors in mitigating global warming. Of the various methods for removing CO2, the NAD-dependent formate dehydrogenase fromCandida boidinii(CbFDH) has been widely used in various biological CO2-reduction systems; however, practical applications of CbFDH have often been impeded owing to its low CO2-reducing activity. It has recently been demonstrated that the NAD-dependent formate dehydrogenase fromThiobacillussp. KNK65MA (TsFDH) has a higher CO2-reducing activity compared with CbFDH. The crystal structure of TsFDH revealed that the biological unit in the asymmetric unit has two conformations,i.e.open (NAD+-unbound) and closed (NAD+-bound) forms. Three major differences are observed in the crystal structures of TsFDH and CbFDH. Firstly, hole 2 in TsFDH is blocked by helix α20, whereas it is not blocked in CbFDH. Secondly, the sizes of holes 1 and 2 are larger in TsFDH than in CbFDH. Thirdly, Lys287 in TsFDH, which is crucial for the capture of formate and its subsequent delivery to the active site, is an alanine in CbFDH. A computational simulation suggested that the higher CO2-reducing activity of TsFDH is owing to its lower free-energy barrier to CO2reduction than in CbFDH.

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Sugishima, Masakazu, Kei Wada, and Keiichi Fukuyama. "Recent Advances in the Understanding of the Reaction Chemistries of the Heme Catabolizing Enzymes HO and BVR Based on High Resolution Protein Structures." Current Medicinal Chemistry 27, no. 21 (June 15, 2020): 3499–518. http://dx.doi.org/10.2174/0929867326666181217142715.

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In mammals, catabolism of the heme group is indispensable for life. Heme is first cleaved by the enzyme Heme Oxygenase (HO) to the linear tetrapyrrole Biliverdin IXα (BV), and BV is then converted into bilirubin by Biliverdin Reductase (BVR). HO utilizes three Oxygen molecules (O2) and seven electrons supplied by NADPH-cytochrome P450 oxidoreductase (CPR) to open the heme ring and BVR reduces BV through the use of NAD(P)H. Structural studies of HOs, including substrate-bound, reaction intermediate-bound, and several specific inhibitor-bound forms, reveal details explaining substrate binding to HO and mechanisms underlying-specific HO reaction progression. Cryo-trapped structures and a time-resolved spectroscopic study examining photolysis of the bond between the distal ligand and heme iron demonstrate how CO, produced during the HO reaction, dissociates from the reaction site with a corresponding conformational change in HO. The complex structure containing HO and CPR provides details of how electrons are transferred to the heme-HO complex. Although the tertiary structure of BVR and its complex with NAD+ was determined more than 10 years ago, the catalytic residues and the reaction mechanism of BVR remain unknown. A recent crystallographic study examining cyanobacterial BVR in complex with NADP+ and substrate BV provided some clarification regarding these issues. Two BV molecules are bound to BVR in a stacked manner, and one BV may assist in the reductive catalysis of the other BV. In this review, recent advances illustrated by biochemical, spectroscopic, and crystallographic studies detailing the chemistry underlying the molecular mechanism of HO and BVR reactions are presented.

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Agnellini, Dario, Mario Pace, Sergio Cinquanta, Claudio Gardana, Pier Giorgio Pietta, and Pier Luigi Mauri. "Characteristics of Bioreactors Made with Urease and Nad Glycohydrolase Reversibly Bound to Immobilized Antibodies." Biocatalysis 6, no. 4 (January 1992): 251–65. http://dx.doi.org/10.3109/10242429209065246.

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PETTERSSON, Gosta, and Hans EKLUND. "Electrostatic effects of bound NADH and NAD+ on ionizing groups in liver alcohol dehydrogenase." European Journal of Biochemistry 165, no. 1 (May 1987): 157–61. http://dx.doi.org/10.1111/j.1432-1033.1987.tb11206.x.

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47

Hu, Yumei, Weidong Liu, Satish R. Malwal, Yingying Zheng, Xinxin Feng, Tzu-Ping Ko, Chun-Chi Chen, et al. "Cover Picture: Structures of Iridoid Synthase fromCantharanthus roseuswith Bound NAD+, NADPH, or NAD+/10-Oxogeranial: Reaction Mechanisms (Angew. Chem. Int. Ed. 51/2015)." Angewandte Chemie International Edition 54, no. 51 (December 3, 2015): 15301. http://dx.doi.org/10.1002/anie.201510890.

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48

Akinterinwa, Olubolaji, and Patrick C. Cirino. "Anaerobic Obligatory Xylitol Production inEscherichia coliStrains Devoid of Native Fermentation Pathways." Applied and Environmental Microbiology 77, no. 2 (November 19, 2010): 706–9. http://dx.doi.org/10.1128/aem.01890-10.

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ABSTRACTAnaerobic glucose oxidation was coupled to xylose reduction in a nonfermentativeEscherichia colistrain expressing NADPH-dependent xylose reductase. Xylitol production serves as the primary means of NAD(P)+regeneration, as glucose is converted primarily to acetate and CO2. The membrane-bound transhydrogenase PntAB is required to achieve the maximum theoretical yield of four moles of xylitol per mole of glucose consumed.

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Liu, Si-Qi, Hongjun Jin, Albert Zacarias, Sanjay Srivastava, and Aruni Bhatnagar. "Binding of Pyridine Nucleotide Coenzymes to the β-Subunit of the Voltage-sensitive K+Channel." Journal of Biological Chemistry 276, no. 15 (January 17, 2001): 11812–20. http://dx.doi.org/10.1074/jbc.m008259200.

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The β-subunit of the voltage-sensitive K+(Kv) channels belongs to the aldo-keto reductase superfamily, and the crystal structure of Kvβ2 shows NADP bound in its active site. Here we report that Kvβ2 displays a high affinity for NADPH (Kd= 0.1 μm) and NADP+(Kd= 0.3 μm), as determined by fluorometric titrations of the recombinant protein. The Kvβ2 also bound NAD(H) but with 10-fold lower affinity. The site-directed mutants R264E and N333W did not bind NADPH, whereas, theKdNADPHof Q214R was 10-fold greater than the wild-type protein. TheKdNADPHwas unaffected by the R189M, W243Y, W243A, or Y255F mutation. The tetrameric structure of the wild-type protein was retained by the R264E mutant, indicating that NADPH binding is not a prerequisite for multimer formation. A C248S mutation caused a 5-fold decrease inKdNADPH, shifted the pKaofKdNADPHfrom 6.9 to 7.4, and decreased the ionic strength dependence of NADPH binding. These results indicate that Arg-264 and Asn-333 are critical for coenzyme binding, which is regulated in part by Cys-248. The binding of both NADP(H) and NAD(H) to the protein suggests that several types of Kvβ2-nucleotide complexes may be formedin vivo.

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50

Kratzer, Regina, and Bernd Nidetzky. "Electrostatic stabilization in a pre-organized polar active site: the catalytic role of Lys-80 in Candida tenuis xylose reductase (AKR2B5) probed by site-directed mutagenesis and functional complementation studies." Biochemical Journal 389, no. 2 (July 5, 2005): 507–15. http://dx.doi.org/10.1042/bj20050167.

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Lys-80 of Candida tenuis xylose reductase (AKR2B5) is conserved throughout the aldo–keto reductase protein superfamily and may prime the nearby Tyr-51 for general acid catalysis to NAD(P)H-dependent carbonyl group reduction. We have examined the catalytic significance of side-chain substitutions in two AKR2B5 mutants, Lys-80→Ala (K80A) and Asp-46→Asn Lys-80→Ala (D46N K80A), using steady-state kinetic analysis and restoration of activity with external amines. Binding of NAD+ (Kd=24 μM) and NADP+ (Kd=0.03 μM) was 10- and 40-fold tighter in K80A than the wild-type enzyme, whereas binding of NADH (Kd=51 μM) and NADPH (Kd=19 μM) was weakened 2- and 16-fold in this mutant respectively. D46N K80A bound NAD(P)H and NAD(P)+ uniformly approx. 5-fold less tightly than the wild-type enzyme. The second-order rate constant for non-covalent restoration of NADH-dependent reductase activity (kmax/Kamine) by protonated ethylamine was 0.11 M−1·s−1 for K80A, whereas no detectable rescue occurred for D46N K80A. After correction for effects of side-chain hydrophobicity, we obtained a linear free energy relationship of log (kmax/Kamine) and amine group pKa (slope=+0.29; r2=0.93) at pH 7.0. pH profiles of log (kcat/Km) for carbonyl group reduction by wild-type and D46N K80A revealed identical and kinetically unperturbed pKa values of 8.50 (±0.20). Therefore the protonated side chain of Lys-80 is not an essential activator of general acid catalysis by AKR2B5. Stabilized structurally through the salt-link interaction with the negatively charged Asp-46, it is proposed to pull the side chain of Tyr-51 into the catalytic position, leading to a preorganized polar environment of overall neutral charge, in which approximation of uncharged reactive groups is favoured and thus hydride transfer from NAD(P)H is strongly preferred. Lys-80 affects further the directional preference of AKR2B5 for NAD(P)H-dependent reduction by increasing NAD(P)H compared with NAD(P)+-binding selectivity.

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