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The progressive decline in the physiological functions during aging leads to various diseases that place a heavy burden on patients, their families and the society as a whole. Due to the increasing average life expectancy, the problems of prevention and treatment of age-related diseases are becoming more and more relevant. As a part of the research on the regulation of the aging program, considerable attention has been focused on a small family of NAD+-dependent deacetylases and deacylases called sirtuins. These proteins are involved in the regulation of numerous intracellular processes, and disruption of their functions plays an important role in the development of various diseases, such as metabolic disorders, pathologies of the cardiovascular system and other organs, musculoskeletal diseases, and neurodegeneration. It is interesting to note that the activity of sirtuins can be modulated to some extent under the influence of pharmacological agents, which makes them promising targets for the prevention and therapy of age-related diseases. The aim of the current review is to summarize the effects of sirtuins on the development and pathogenesis of neurodegenerative diseases, taking into account the reported clinical trials on the pharmacologic agents affecting the sirtuins’ activity.

Objective: Evaluation of the relationship between the activity of proteolytic enzymes (cathepsin D and calpains) and the dynamics of the fluorescence intensity of the coenzymes nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) in the rats' skeletal muscles in relation to the time of death. The proteolytic activity of enzymes in rat skeletal muscle was determined at the postmortem time points corresponding to the most significant changes in the dynamics of coenzymes NADH and FAD fluorescence intensity. The proteolytic enzymes activity was found to be low during the period of increasing intensity of NADH fluorescence observed within 3 hours after death. An increase in the activity of proteolytic enzymes was registered in 4.5 hours after death which corresponds to the initial point of decrease in NADH fluorescence intensity. In 24 hours post-mortem, corresponding to increased FAD fluorescence intensity a significant decrease in the activity of calpains was found. The results of the study suggest that the nature of the postmortem dynamics of the fluorescence intensity of coenzymes is largely due to the peculiarities of intracellular proteolysis. The study results suggest that the pattern of post mortem changes in coenzyme fluorescence intensity is largely attributable to the specifics of intracellular proteolysis. The relationship between coenzyme fluorescence and molecular mechanisms of cell death confirms the viability and feasibility of laser-induced spectroscopy for post-mortem changes assessment when determining the time of death.

Background: The regulatory effect of thyroid hormones on the metabolism of the immune system cells (activation of oxidative processes, separation of oxidative phosphorylation and increased protein synthesis) depends on their number. Changes in the activity of intracellular enzymes in Graves’ disease (GD) can determine the mechanisms of maintaining autoimmune inflammation in relapse of the disease. The exact role of NAD(P)-dependent dehydrogenases in the development and maintenance of immune response in GD is still poorly investigated., Aims: To study the activity of NAD(P)-dependent dehydrogenases in lymphocytes of peripheral blood in patients with manifestation and relapse of GD to clarify the mechanisms of development and progression of the autoimmune process., Methods: A single-center, cohort, prospective, continuous, observational, open-label, controlled trial was conducted to evaluate the lymphocytes NAD(P)-dependent activity in 151 women with GD and hyperthyroidism, mean age 40.7±13.2, 52 (37.14%), who were on follow-up at the endocrinology center of Krasnoyarsk Regional clinical hospital from 2016 to 2019. The NAD(P)-dependent dehydrogenases activity measured using biochemiluminescence method., Results: In patients with newly diagnosed of GD, relative to the control values and levels detected in relapse group we observe the increase of G6PDH and decrease of NADH-LDH. In GD relapse group compare to the control range in blood lymphocytes decreases the activity of LDH and NAD(P)-ICDH. In patients with newly diagnosed GD, two positive сorrelation were found: between fT3 level and MDG activity (r=0.90, p=0.037), and between fT4 level and NAD(P)-ICDH activity (r=0.82, p=0.007). In patients with relapse of GD positive relationships between the concentration of TSH and the activity of LDH (r=0.73, p=0.039), and MDH (r=0.93, p=0.002), as well as in a pair of fT4 and NADGDH (r=0.70, p=0.036) were revealed., Conclusion: The established differences in the activity of NAD(P)-dependent dehydrogenases in peripheral blood lymphocytes in patients with manifestation and relapse of GD can reflect in the first case the response of immune cells to a functional-regulatory signal with the development of hyperthyroidism, and in the second case, adaptive changes with the progression of autoimmune process.

The intrinsic fluorescence of reduced nicotinamide adenine dinucleotide (NADH) and oxidized flavoproteins in animals and humans in the norm and in the development of pathological processes was studied. The results of the use of a fluorescent analysis in cancer diagnosis are represented.

In the process the cultivation of H. influenzae, type b, in semisynthetic nutrient medium with aminopeptide base the growth of the bacteria and the synthesis of capsular polysaccharide were shown to depend on the concentrations of aminopeptide, nicotinamide adenine nucleotide (NAD) and hemin. An increase in the concentrations of NAD and hemin stimulated the growth of H. influenzae and inhibited the synthesis of capsular polysaccharide. Similar effect was observed in the simultaneous increase of NAD and hemin concentrations. At elevated concentrations of NAD and hemin and the content of aminopeptide equal to 350 mI/l the maximum weight of biomass was achieved. The increase of hemin concentration had no influence on the growth of H. influenzae, type b, and the synthesis of capsular polysaccharide.

Human erythrocyte catalase activity was studied involving the peroxidase reaction with ethanol and the reverse alcohol dehydrogenase reaction. The adequate kinetic parameters of the reaction were obtained under mild conditions of hemolysate preparation. Estimation of catalase activity in series of hemolysates enabled us to measure the activity values near 220.0 kU/ml of erythrocytes which corresponded to those in literature. Adaptation of the superoxide dismutase activity evaluation in erythrocytes was carried out using the basic system NADH-phenazine methasulfate-tetrazolium blue and the analyzer FP-901 equipped for nine simultaneous measurements. The rate of base reactions was plotted and the linear correlation was found between the reaction inhibition per cent and content of erythrocyte hemolysate and of commercially available preparation of superoxide dismutase. The procedures are simple and reproducible and may be used in routine studies of antioxidants.

The structure of the active center of glyceraldehyde-3-phosphate dehydrogenase and the arrangement of subunits in the tetrameric molecule is delineated. The mechanism of cooperative effects in the oligomer is considered, and the involvement of various regions of the active center and of different-subunit contact area in the realization of the cooperative phenomena is discussed. A special attention is paid to the effect of NAD+ bound to one of the subunits of the tetramer on the structure of an adjacent subunit and to the problem of the participation of the coenzyme in the creation of anion-binding sites of the enzyme. The conditions of reversible dissociation of the tetrameric apoenzyme molecule into dimers are depicted, and the role of NAD+ in the organization of the quaternary structure of the dehydrogenase is discussed. The problem of catalytic activity of the dimeric form of the enzyme is argued.

The kinetic method and selective chemical modification have been used in studies of the kinetic manifestations of active site interactions in D-glyceraldehyde-3-phosphate dehydrogenase (GAP dehydrogenase). The reactions of glyceraldehyde and glyceraldehyde-3-phosphate oxidation were studied in the absence of substrate excess. In support of the data obtained previously it was shown that only a part of the tightly bound NAD molecules can be reduced after substrate addition. "Partial reducibility" is observed at various degrees of saturation of the enzyme with NAD involving a single NAD molecule per tetrametric enzyme. These facts can hardly be explained by assumption of functional non-equivalence of active sites, whether induced by coenzyme or preexisting in the apoenzyme. It was proven by selective alkylation of the catalytic SH groups that "partial reducibility" is due to the circumstance that equilibrium in the system under investigation is established at nearly equal NAD and NADH concentrations. A plot of initial reaction rates versus NAD concentration (at non-saturating substrate concentrations) gives S-shaped curves; this is explained by considerable enzyme activation upon saturation of the fourth site with coenzyme. After modification of three active sites with iodoacetate the S-shape of the curve disappeared. This fact leads to the conclusion that active site interactions are required for formation of the S-shaped curves. The activity of a single site functioning in the modified enzyme reached values equal to those of the active sites in the native enzyme in the fully activated state. A model is proposed which can explaine the variations in mode of enzyme activation in the native and modified states. It is suggested that the surroundings of all four SH groups must be altered in order to activate the enzyme; such changes can be induced either by alkylation of the SH groups or by NAD binding. Evidence is presented that important functional properties of GAP dehydrogenase cannot be elucidated at low enzyme concentrations and with excess of substrates: three active sites are saturated under such conditons and practically inactive, and the fourth site obeys Michaelis - Menten kinetics.

Mechanisms of NADH oxidation in the presence of flavines in the light under aerobic and anaerobic conditions has been studied by spectrophotometry method and by registering the kinetics of changes in pH, luminescence and oxygen content in solution. It is shown that singlet oxygen O2* generated by triplet flavine may be an agent that immediately oxidizes NADH under aerobic conditions. The rate constant of the reaction of O2* with NADH accounts for about 1.9 . 10(9) M-1 s-1 and maximum quantum yield of NADH photooxidation in the presence of flavine mononucleotide is 0.7. During aerobic oxidation of NADH the flavine molecules function as photosensitizers rather than as carriers of reduced equivalents.

The generation of H2O2 in skeletal muscle mitochondria during the oxidation of NAD-dependent substrates and succinate is initiated by antimycin A but not by rotenone, which points to H2O2 formation at the respiratory chain site between the rotenone and antimycin blocks. The O2-/H2O2 ratio for alpha-ketoglutarate and succinate oxidation is approximately 1.4, which suggests that in skeletal muscle mitochondria H2O2 is predominantly formed via the superoxide radical generation. Heart and skeletal muscle mitochondria appeared to have the similar values of Vmax for H2O2 production; the catalase activity in skeletal muscle mitochondria is much lower.

Mitochondria of white rat brain increased the respiration on succinate in response to ADP addition; in the presence of after NADH the respiration remained unchanged or decreased ofter addition ADP. When organelles were suspended in water distilled in the concentration of 3 mg of protein/ml and kept at melting ice temperature for 24 hours the response of mitochondria to ADP was not changed. Stechiometric relation between the number of electron of the oxidized substrate and absorbed by oxygen depended on ADP during succinate oxidation and did not change on NADH. ADP phosphorylation is suggested to proceed on the stage of the substrate dehydrogenation, rather than on the cytochrome part of the respiratory chain.

A mathematical model explaining the mechanism of autooscillation generation in the lower part of the glycolytic system is suggested. The model is based on substrate inhibition of glyceraldehydephosphatedehydrigenase (GAPDH) with glyceraldehydephosphate (GAP). Pyrimidinenucleotides (NADplus and NADH) are shown not to play an important role in the given oscillation mechanism and can not be considered to simplify the model.

The kinetics of enzymatic oxidation of ethanol in the presence of alcohol dehydrogenase within a wide range of ethanol and NAD concentrations (pH 6.0--11.5) were studied. It was shown that high concentrations of ethanol (greater than 0.7--5 mM, depending on pH) and NAD (greater than 0.4--0.8 mM) activate alcohol dehydrogenase from horse liver within the pH range of 6.0--7.9. A mechanism of activation based on negative cooperativity of ADH subunits for binding of ethanol and NAD was proposed. The catalytic and Michaelis constants for alcohol dehydrogenase were calculated from ethanol and NAD at all pH values studied. The changes resulting from the subunit cooperativity were revealed. The nature of ionogenic groups of alcohol dehydrogenase, which affect the formation of complexes between the enzyme and NAD and ethanol, and the rate constants for catalytic oxidation of ethanol was assumed. The biological significance of the enzyme capacity for activation by high concentrations of ethanol within the physiological range of pH in the blood under excessive use of alcohol is discussed.

Binding of Ca2+ ions by EGTA is established to increase the oxoglutarate dehydrogenase complex K'm for 2-oxoglutarate up to 25 mM in spite of the Mg2+ ions presence in the medium. The maximum reaction rate remains unchanged. Addition, besides EGTA of an equimolar Ca2+ amount to the medium induces a more than 100-fold decrease in K'm. A positive effect of Ca2+ ions is intensified by ADP. Ca2+ counteracts the inhibition of the oxoglutarate dehydrogenase complex activity by NADH. When chelating Ca2+ by EGTA with NADH available, a nonhyperbolic dependence of the reaction rate on the 2-oxoglutarate concentration is observed. When Ca2+ is absent, signs of a positive cooperative interaction of the enzyme with ADP and NADH are observed under conditions when 2-oxoglutarate concentration is much lower than the saturating one.

The kinetic behaviour of highly purified malate dehydrogenase (EC 1.1.1.37) from grape vine leaves has been studied. The curves of the dependence of the initial velocity (v) on oxaloacetate and NADH concentrations at low concentration of the enzyme are hyperbolic, while at relatively high concentrations of the enzyme they are S-shaped (nH = 2 and nH = 1.7 for oxaloacetate and NADH, respectively). The dependence of v upon malate concentrations at low enzyme and substrate concentrations obeys the Michaelis--Menten equation (nH = 1.0); at relatively high concentration of the enzyme at any substrate concentrations of the enzyme it is characterized by "negative" kinetic cooperativity. With respect to NAD malate dehydrogenase at low enzyme concentrations reveals "positive" cooperativity (nH = 2.5), but at relatively high concentrations shows a hyperbolic dependence. The specific malate dehydrogenase activity determined in both directions, i. e. reduction of oxaloacetate and oxidation of malate, strongly depends on the enzyme concentration. At low and relatively high concentrations of the enzyme the specific malate dehydrogenase activity sharply decreases. Therefore malate dehydrogenase can be attributed to reversibly associating oligomeric allosteric enzymes.

A dependence is established for the activity of NADP-dependent isocytrate dehydrogenase and malate dehydrogenase as well as of NAD-malate dehydrogenase on the carbonic acid level. When the biocarbonate concentration in rabbit blood and tissues rise, the activity of cytoplasmic NADP-isocytrate dehydrogenase and NADP-malate dehydrogenase of the liver lowers. The analogous regularity is observed in the in vitro experiments when the bicarbonate concentrations in the medium rises up to 40 mM (within the physiological limits). The activity of NAD-malate dehydrogenase in the soluble fraction of the rabbit liver and kidney increases with the bicarbonate level within the same limits. The found dependence was confirmed in experiments with the enzyme crystalline preparations.

The afterglow of some organisms is registered in the region of 460--540 nm at excitation in the 365 nm region. Apparently this effect is due to NAD and flavin containing coferments of proteins. The afterflow of NAD and riboflavin is also registered in thin films of albumin at excitation in 365 nm. The afterflow of NAD and riboflavin in thin protein films is similar to that spectrum of freezedried organisms' when the concentrations of these components are close to their concentrations in the cell.

Isoenzymes NAD-and NaDP MDH were detected in the cardiac muscle of rabbits by disc electrophoresis in polyacrylamide gel. Alloxan diabetes proved to be accompanied by a significant reduction in the activity of mitochondrial NADP MDH (in the reaction of malic decarboxylation) and its increase in cytozol. The activity of NAD-MDH (in the reaction of oxyacetate reduction) was also decreased in various isoenzymes in the myocardium (particularly in the mitochondria) in diabetes. Insulin restored the correlation of the activities of the isoenzymes NAD- and NADP-MDH in the cytostructures of the myocardium disturbed in diabetes.

The hyperbolic dependence of the initial rate of the adrenal pyruvate dehydrogenase complex-catalyzed reactions on pyruvate, CoA and NAD concentrations was established. The Lineweaver--Burk plots of v0 against one substrate concentration at constant unsaturating concentrations of other substrates represent families of parallel lines. The Km values for pyruvate, CoA and NAD are 0,017, 0.005 and 0.030 mM, respectively. CoA-SAc was shown to compete with CoA (Ki=0.067 mM) whereas NADH--with NAD (Ki=0.023 mM). Both CoA-SAc and NADH are uncompetitive inhibitors with respect to pyruvate. The inhibition of CoA-SAc against NAD is of a mixed type, while that of NAD against CoA is non-competitive. The results obtained are in agreement with the kinetic model of a three-site "ping-pong" mechanism.

The character of allosteric inhibition of glutamate dehydrogenase by GTP was studied. The derivative of the enzyme not capable of being polymerized was taken as a model. It was shown that: in the absence of NADH every protomer of this derivative can bind one molecule of GTP; in the presence of NADH the additional binding site for GTP was induced; the modification of the enzyme derivative by pyridoxal-5-phosphate in the presence of NADH and alpha-ketoglutarate blocked the NADH-induced GTP binding site and the disappearance of positive kinetic cooperativity induced by GTP was observed; to achieve the inhibitory action of GTP the binding of the effector to only one (NADH-induced) site was enough; the role of GTP binding to the NADH-induced site is to provide better affinity of the effector to the "inhibitory" centre; the positive kinetic cooperativity of inhibition of glutamate dehydrogenase by GTP depends probable on the cooperative character of interaction between the two molecules of GTP to each protomer of the enzyme.

The study of the flavin mononucleotide (FMN)-reduced nicotinamide adeninedinucleotide (NADH) reaction was carried out both under aerobic and anaerobic conditions, using spectrophotometric and titrimetric methods. The consumption of NADH was shown to exceed two times the consumption of FMN in the anaerobic reaction and the rate constant in the aerobic reaction was found to be about 4 times of that of the anaerobic reaction. Moreover, the replacement of anaerobic conditions by aerobic ones at pH 5.0 resulted in a considerable increase of proton consumption rate in the reaction course. The data obtained are contradictory to the generally accepted hypothesis of hydrid-ion transfer in the reaction of NADH oxidation. It was assumed that this reaction proceeded through a homolytic pathway.

The quaternary structure and some kinetic properties were studied for NAD-kinase from the rabbit skeletal muscles. The molecular weight of the 150-300-fold purified enzymic preparation was determined by separation in the Sephadex G-200 thin layer, by means of Sephadex G-200 column gel-filtration and by the method of electrophoresis in the gradient of polyacrylamide gel concentration. Some molecular forms of NAD-kinase with a molecular weight of 31000-305000 are found in the enzymic preparation and possibility to change from one form to another is shown. On the basis of the established quaternary structure and complex kinetic characteristics of the enzyme a conclusion is drawn on the existence of the rabbit skeletal muscle NAD-kinase as an equilibrium system of the oligomeric forms possessing different catalytic activity and consisting of different combinations of subunits with a molecular weight of 31000.

Metabolic capacity of the Krebs cycle was limited in liver tissue of rats with experimental thermic burns of the IIIa-IIIb grade, involving 25-30% of a body surface; the phenomenon was primarily manifested in a decrease in the citrate synthesis, which occurred due to a decrease in content of citric acid and to decrease in the rate of 2-14C-pyruvate and 2-14C-acetate incorporation into citric acid. At the same time, impairment of alpha-ketoglutaric acid metabolism was found: specific radioactivity of the substance, after incorporation of 2-14C-pyruvate, was decreased and amount of the metabolite--increased. Simultaneously, activity of isocitrate- and malate dehydrogenases was decreased in liver mitochondria. In burns these impairments might be important for decrease of glucose energy potential in liver tissue and for alteration of other metabolic reactions.

On the bases of histochemical enzymatic studies and morphometric investigations, some differences were revealed between cross-striated esophageal muscular tissue and other skeletal muscles of mammals. A peculiar feature of the esophageal musculature is prevalence of unitypical fibres with small diameter and possessing high activity of oxidating enzymes. According to these signs, esophageal myons can be ascribed to the first type of muscular fibres. Simultaneously, a high activity of myofibrillar ATPh is revealed in them. Thus, according to histochemical indices, cross-striated esophageal muscular fibres of mammals are quick and slowly fatiqued fibres.

A direct measurement of the electrogenic activity of purified mitochondrial transhydrogenase has been carried out. For this purpose beef heart transhydrogenase was isolated and reconstituted with phospholipids to form proteoliposomes. The transhydrogenase proteoliposomes were incorporated into a membrane filter impregnated with a decane solution of phospholipids. It was shown that the addition of substrates of either forward (NADPH and NAD+) or reverse (NADH and NADP+) transhydrogenase reaction gives rise to formation of electric potential difference across the proteoliposome-treated membrane filter. The electric vector depends on the direction of the reaction. The proteoliposome-supplemented compartment charges negatively in the case of the reverse one. The addition of the reaction products after substrate equalizes the potentials. The transhydrogenase-treated membrane retains the ability to the transhydrogenase-linked electrogenesis after removal of an excess of non-incorporated proteoliposomes.

Electrophoresis in polyacrylamide gel slabs has been used to study the isoform composition and substrate specificity of alcohol dehydrogenases in the embryo and young seedlings of the diploid wheat Triticum monococcum L., the tetraploid T. dicoccon (Schrank) Schuebl and the hexaploid T. spelta L. Three alcohol dehydrogenases of different substrate specificity and developmental pattern were distinguished: a) the NAD-dependent alcohol dehydrogenase, catalyzing the oxidation of different primary and secondary aliphatic and aromatic alcohols, as well as certain compounds with several hydroxyl groups (tris, triethanolamin) and revealing, after electrophoresis, one major band in the diploid wheat and three bands in both polyploid wheats; b) the NADP-dependent aromatic alcohol dehydrogenase (substrate--cinnamic alcohol), revealing, after electrophoresis, one major fast moving band in the diploid wheat and two bands in polyploid wheats; c) an aromatic alcohol dehydrogenase (2-3 bands after electrophoreis) with no specificity to the cofactors (NAD or NADP).

The cells of Achromobacter parvulus, strain 1T, when grown in a methanol-containing medium, have two formate dehydrogenases, i.e. NAD-linked formate dehydrogenase and the formate dehydrogenase reducing the ferricyanide and tetrazolia. Only the latter enzyme was found in the cells grown in a medium with glycerol as a carbon source. These enzymes differ with respect to Km for formate and antigenic specificity. Km for formate oxidation by the cells of A. parvulus is lower than for formate of the NAD-dependent formate dehydrogenase and is equal to Km for the enzyme reducing artificial electron acceptors. The results obtained are discussed in terms of the existence of two cytochrome oxidase systems in the methylotrophic bacteria, differing in their sensitivities to the inhibition by formate.

The isozymes of malate dehydrogenase (MDH) were studied by means of electrophoresis in polyacrilamide gel in Acetabularia crenulata and A. mediterranea. The isozyme profile of MDH was shown to be variable in different parts of the plant. Distinct differences in isozyme profiles of MDH between A. crenulata and A. mediteranea were found when studying the cell fractions which consisted mainly of chloroplasts. The chloroplast fraction of A. mediterranea contained 8 isozymes which form 2 groups with different electrophoretic mobility. The chloroplast fraction of A. crenulata contained 9 isozymes. All the isozymes of the first group were common for both the species under study.

The multiplicity of NAD-dependent glutamate dehydrogenase (GDH) was studied in the liver and femoral muscle of 30, 60 and 108 days old pig embryos by the method of discelectrophoresis in polyacrilamide gel. The GDH was shown to be presented in the tissues under study by 3--4 multiple molecular forms. Specific ratios of the multiple GDH forms were established in the tissues under study at different stages of embryogenesis.

Illumination of NADH and NADPH by UV-light in the absence of oxygen resulted in the reduction of ferredoxin or methyl-viologen to cation-radical and under prolonged illumination to dihydrodipyridyl. The reaction may by accompanied by triplet and singlet exitation of NADH. It was shown that hematoporphyrin in aqueous solution photosensitized the reaction of NADH oxidation by ferredoxin and methylviologen to the visible region of the spectrum. Under light excitation the redox potentials of NADH and NADPH were increased up to the level exceeding the potential of hydrogen electrode. Illumination of NADH and NADPH by UV-light in the presence of bacterial hydrogenase resulted in hydrogen evolution. The reaction of hydrogen evolution could be sensitised towards the visible region of the spectrum by chlorophyll or chloroplasts.

The properties of N-methylglutamate dehydrogenase, a new enzyme of methylamine metabolism in a facultative methylotroph Pseudomonas methylica, strain 2, were investigated. The enzyme was strictly dependent on the NAD presence and was not connected with particles in cell-free preparations. The enzyme appeared to be incucible and its activity increased after the growth of the cells in a medium containing methylamine.