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Query: EC:1.2.1.13 (glyceraldehyde-3-phosphate dehydrogenase)
 6,511 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The reduction of benzaldehyde and p-nitrobenzaldehyde by NADH, catalyzed by horse liver alcohol dehydrogenase (LADH), has been found to be faster when NADH is bound to glyceraldehyde-3-phosphate dehydrogenase (GPDH) than with free NADH. The rate of reduction of aldehyde substrate with GPDH-NADH follows a Michaelian concentration dependence on GPDH-NADH. The reaction velocity is independent of GPDH concentration when [GPDH] greater than [NADH]total. The Km for GPDH-NADH is higher than that for free NADH. The reaction velocities in the presence of excess GPDH over NADH cannot be accounted for on the basis of the free NADH concentration arising from dissociation of the GPDH-NADH complex. These observations suggest that transfer of NADH from GPDH to LADH proceeds through the initial formation of a GPDH-NADH-LADH complex. Arguments for a direct enzyme-coenzyme-enzyme transfer mechanism are substantiated and quantitated both by steady-state kinetic studies and by determinations of all of the appropriate enzyme-coenzyme equilibrium dissociation constants. In contrast, over a similar concentration range, the complex lactate dehydrogenase (LDH)-NADH is not a substrate for the LADH-catalyzed reductions. Likewise, the LADH-NADH complex is not a substrate for the LDH-catalyzed reduction of pyruvate.
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PMID:Direct transfer of reduced nicotinamide adenine dinucleotide from glyceraldehyde-3-phosphate dehydrogenase to liver alcohol dehydrogenase. 638 29

A simple screening procedure for the detection of glucose-phosphate isomerase (GPI), phosphofructokinase (PFK), aldolase (AL) and glyceraldehyde-3-phosphate dehydrogenase (GAPD) deficiencies in blood, is described. These enzymes catalyze the second, third, fourth, and sixth reactions in the Embden-Meyerhof pathway. The procedure is based on the conversion of glucose-6-phosphate to 1,3-diphosphoglycerate (1,3-DPG) which is catalyzed by the sequential action of the GPI, PFK, AL and GAPD. The presence of the enzyme activities is visually estimated by the reduction of NAD+ (non-fluorescent) to NADH (fluorescent) which occurs when 1,3-DPG is formed. Absence of fluorescence indicates the deficiency of anyone of the four enzymes, which are specified by using separately the PFK, AL and GAPD respective substrates.
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PMID:A simple screening procedure for glucose phosphate isomerase, phosphofructokinase, aldolase and glyceraldehyde-3-phosphate dehydrogenase deficiencies. 646 Apr 65

The metabolism of [2-3H]lactate was studied in isolated hepatocytes from fed and starved rats metabolizing ethanol and lactate in the absence and presence of fructose. The yields of 3H in ethanol, water, glucose and glycerol were determined. The rate of ethanol oxidation (3 mumol/min per g wet wt.) was the same for fed and starved rats with and without fructose. From the detritiation of labelled lactate and the labelling pattern of ethanol and glucose, we calculated the rate of reoxidation of NADH catalysed by lactate dehydrogenase, alcohol dehydrogenase and triosephosphate dehydrogenase. The calculated flux of reducing equivalents from NADH to pyruvate was of the same order of magnitude as previously found with [3H]ethanol or [3H]xylitol as the labelled substrate [Vind & Grunnet (1982) Biochim. Biophys. Acta 720, 295-302]. The results suggest that the cytoplasm can be regarded as a single compartment with respect to NAD(H). The rate of reduction of acetaldehyde and pyruvate was correlated with the concentration of these metabolites and NADH, and was highest in fed rats and during fructose metabolism. The rate of reoxidation of NADH catalysed by lactate dehydrogenase was only a few per cent of the maximal activity of the enzymes, but the rate of reoxidation of NADH catalysed by alcohol dehydrogenase was equal to or higher than the maximal activity as measured in vitro, suggesting that the dissociation of enzyme-bound NAD+ as well as NADH may be rate-limiting steps in the alcohol dehydrogenase reaction.
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PMID:The reversibility of cytosolic dehydrogenase reactions in hepatocytes from starved and fed rats. Effect of fructose. 647 25

Spinach-leaf ribulose-5-phosphate kinase catalyzes the reaction of (Rp)-[beta, gamma-18O, gamma-18O]adenosine 5'-(3-thiotriphosphate) with ribulose 5-phosphate to form ribulose 1-[18O]phosphorothioate 5-phosphate. This product is incubated with CO2, Mg2+, and ribulose-bisphosphate carboxylase to form the [18O]phosphorothioate of D-glycerate. Reduction of this material using phosphoglycerate kinase/ATP, glyceraldehyde-3-phosphate dehydrogenase/NADH, triose-phosphate isomerase, and glycerol-phosphate dehydrogenase/NADH produces glycerol 3-[18O]phosphorothioate, which is subjected to ring closure using diethylphosphorochloridate. This in-line reaction produces a diastereoisomeric mixture of glycerol 2,3-cyclic phosphorothioates. 31P NMR spectroscopy was used to analyze the 18O content of the products. The anti-diastereoisomer, which is the major isomer formed and corresponds to the downfield 31P NMR signal (Pliura, D.H., Schomburg, D., Richard, J.P., Frey, P.A., and Knowles, J.R. (1980) Biochemistry 19, 325-329), retains the 18O label. This observation indicates that the ribulose-5-phosphate kinase reaction proceeds with inversion of configuration at phosphorus. The reaction is, therefore, unlikely to involve the participation of a covalent phosphoryl-enzyme intermediate.
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PMID:The stereochemical course of the ribulose-5-phosphate kinase-catalyzed reaction. 649 Jun 43

Infusion of 2 mM ethanol into perfused liver from fed rats increased the rate of oxygen uptake concomitant with the decrease in the rate of glycolysis (lactate + pyruvate production). A linear correlation (r = 0.92) was observed between the increase in the rate of oxygen uptake and the decrease in the rate of lactate + pyruvate production determined on the whole organ by the difference between influent minus effluent concentration. Miniature oxygen electrodes (tip diameter, 50 micron) were then placed on periportal or pericentral regions of the lobule on the liver surface, and local rates of oxygen uptake were determined by stopping the flow of perfusate and monitoring the rate of decrease of oxygen concentration ('stopped-flow oxygen uptake technique'). During perfusion in the anterograde direction, ethanol infusion (2 mM) increased rates of oxygen uptake about twofold more in pericentral (15 mumol X g-1 X h-1) than in periportal (7 mumol X g-1 X h-1) regions of the liver lobule in livers from well-fed rats. In contrast, ethanol did not affect the rate of oxygen uptake significantly in either region of the liver lobule in livers from fasted rats. Glucose (30 mM) decreased oxygen concentrations initially in both regions of the liver lobule when infused into livers from fasted rats perfused in the anterograde direction. Subsequently, glucose increased the oxygen concentration in pericentral but not periportal regions of the liver lobule. This increase in regional oxygen concentration correlated temporally (r = 0.99) with increases in rates of glycolysis. The addition of ethanol in the presence of glucose reduced the rate of lactate + pyruvate production and increased the rate of oxygen uptake predominantly in pericentral regions. These data are consistent with the following interpretation. Ethanol metabolism elevates NADH in both periportal and pericentral regions of the liver lobule causing redox inhibition of glyceraldehyde-3-phosphate dehydrogenase and decreased rates of glycolytic ATP synthesis. The ADP not phosphorylated in the cytosol then moves into the mitochondrion and stimulates oxygen uptake. Since ethanol and glucose elevated oxygen uptake to a greater extent in pericentral regions of the liver lobule, it is concluded that glycolysis predominates in hepatocytes located proximal to the central vein during perfusion in the anterograde direction. When similar experiments were performed with perfusion in the retrograde direction, glycolysis was localized in periportal regions of the liver lobule.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Predominance of glycolysis in pericentral regions of the liver lobule. 671 31

The solubilization of lactate dehydrogenase (LDH), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and alpha-glycerophosphate dehydrogenase (GAPDH) was studied in pressed muscle as a function of ionic strength and NADH concentration. The results indicate that these factors affect the binding-solubilization of LDH and GAPDH in a similar way to their effect in dilute homogenized tissue. Alpha-glycerophosphate dehydrogenase was included as a typical soluble enzyme, since we have been unable to demonstrate its binding to subcellular fractions under any conditions. As with homogenized tissue, LDH was less susceptible to solubilization by ionic strength than GAPDH. It was demonstrated that LDH isozymes richer in heart-type subunits were more easily removed from muscle by centrifugation-imbibition than isozymes richer in the muscle-type subunits. This was interpreted as indicating that binding of the enzyme to subcellular structures was a major factor in the restricted removal of these enzymes from muscle, since only the muscle-type subunit is capable of binding to subcellular particles. It was further demonstrated that LDH could be taken up into muscle tissue, depleted in the enzyme, against an apparent concentration gradient. This was also interpreted as binding of the enzyme to the particulate structure of the muscle. Furthermore, this uptake of LDH occurred under conditions of ionic strength (0.25) and pH (7.5) that would prevent binding of the enzyme to the particulate fraction of a dilute suspension of homogenized muscle tissue. Thus, physiological conditions of pH and ionic strength do not necessarily induce solubilization of chicken breast muscle LDH in situ. Data obtained with dilute tissue homogenates, therefore, may not necessarily be easily and safely extrapolated to conditions in situ.
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PMID:A study of binding-solubilization of some glycolytic enzymes in striated muscle in situ. 678 May 75

1. The hybridization of rabbit muscle and yeast glyceraldehyde-3-phosphate dehydrogenase (D-glyceraldehyde-3-phosphate:NAD+ oxidoreductase (phosphorylating), EC 1.2.1.12) was used to study the involvement of subunit interactions in NAD+ and NADH binding by these enzymes. 2. In the presence of 1 mM NAD+ or NADH no hybrid formation was observed with our preparations of the two enzymes. 3. The inhibition by NADH of the hybrid formation is shown to be a consequence of an unfavourable equilibrium of the hybridization process in the presence of NADH. 4. The inhibition by NAD+ of the hybrid formation is shown to be a consequence of both a shift in the equilibrium, as in the case of NADH, and a decrease in the rate of the dissociation of the enzymes. 5. The dimer of the yeast enzyme binds NAD+ or NADH with equal affinity irrespective of whether it is combined with another yeast dimer in the yeast tetramer or with a rabbit muscle dimer in the hybrid. 6. The binding of NAD+ and NADH to the dimer of the rabbit muscle enzyme is stronger in the rabbit muscle tetramer than in the hybrid; this explains the shift in the equilibrium of the hybridization process caused by these nucleotides. 7. Alkylation of the rabbit muscle enzyme with iodoacetate does not influence the hydridization process in the absence of nucleotides. 8. After alkylation of the rabbit muscle enzyme NADH cannot cause a large shift in the equilibrium of the hybridization process. 9. In accordance with this it was found that the binding of NADH (and NAD+) to the rabbit muscle enzyme is weakened by alkylation, whereas the binding of NADH to the alkylated rabbit muscle subunits is not affected strongly by the hydridization. 10. An attempt is made to combine the effects of nucleotides on the hybridization properties of the yeast enzyme and the alkylated or unalkylated rabbit muscle enzymes with the binding properties of all tetrameric species involved in the hybridization processes in a thermodynamic description of nucleotide binding and subunit interactions.
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PMID:Subunit interactions in glyceraldehyde-3-phosphate dehydrogenases. Their involvement in nucleotide binding and cooperativity. 700 89

Under conditions which cause dissociation of soluble tetrameric glyceraldehyde-3-phosphate dehydrogenase (D-glyceraldehyde-3-phosphate:NAD+ oxidoreductase (phosphorylating), EC 1.2.1.12) into inactive dimers, immobilized apoenzymes from yeast and rat skeletal muscle coupled to CnBr-activated Sepharose via one subunit retain 50% of matrix-bound protein with unaltered specific activity. The solubilized dissociated species are inactive. Two molecules of NAD+ (NADH) firmly bound to the immobilized rat muscle tetramer can prevent the dissociation. Immobilized dimer was demonstrated to bind one molecule of coenzyme with high affinity. Using various combinations of immobilized and soluble rat muscle and yeast dimers, we succeeded in reconstituting tetramers, containing one molecule of NAD+ bound either to a matrix-linked or to a non-covalently bound dimer. In the latter case, the dissociation of the tetramer was completely prevented. This suggests that the binding of a single coenzyme molecule is sufficient to stabilize the interdimeric contacts provided the neighbouring dimer is stabilized independently. Such stabilization is produced by the covalent binding of one of the subunits comprising the dimer to the matrix. The structure of the dimer as a whole becomes resistant to the action of the dissociating agent. The effect appears to be cooperative and similar to that of NAD+ or NADH. The dissociation of the immobilized tetramer is, most likely, the result of conformational changes, affecting the structure of the non-covalently bound dimer. Any factor, capable of preventing these changes, would stabilize the interdimeric contacts. The latter conclusion is substantiated by the effect of specific antibodies, which prevent the dissociation of the immobilized tetramer by forming a complex with the dimer, non-covalently bound to the matrix. The evidence obtained in the present investigation supports the conclusion that the isolated dimer of glyceraldehyde-3-phosphate dehydrogenase represents a relatively independent structural and functional 'unit' of the enzyme. It can be stabilized in a catalytically active form by interactions other than those involved in inter-dimeric contacts in the tetramer. The kinetics of the association of immobilized and soluble dimers have been studied. Association rate constants were determined for homologous (yeast-yeast, rat-rat) and heterologous (yeast-rat, yeast-rabbit) dimer combinations. The binding of one molecule of specific antibody to the immobilized dimer was shown to increase the rate constant of association.
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PMID:Study of subunit interactions in immobilized D-glyceraldehyde-3-phosphate dehydrogenase. 700 90

A bioluminescent assay for determination of glycerol using bacterial NADH-linked luciferase was developed and successfully applied to measurement of glycerol release from human fat cells. The procedure is based on enzymic conversion of glycerol to 3-phosphoglycerate, which is irreversible in the presence of arsenate, and subsequent determination of NADH formed in the glycerol-phosphate- and glyceraldehyde-3-phosphate dehydrogenase reactions respectively. Bioluminescent determination of glycerol is about 100 times more sensitive than conventional spectrophotometry, thus permitting more than 100 determinations to be carried out on needle biopsy specimens.
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PMID:Microdetermination of glycerol using bacterial NADH-linked luciferase. 707 66

The evidence for equivalent catalytic sites in tetrameric glyceraldehyde-3-phosphate dehydrogenase from rabbit muscle has been re-examined and found to be insufficient to exclude alternating or reciprocating sites models. Using a column centrifugation technique, lower limits have been set on the rates of binding and release of coenzyme, and on the ratio of the affinities of NAD+ and NADH. The binding to acyl enzyme has also been examined. The tightly bound NAD+ has been found to be reduced preferentially and kinetically competently when glyceraldehyde 3-phosphate is added, demonstrating the nonequivalence of the sites in the transient reduction of NAD+. The rate of release of the NADH formed rapidly from tightly bound NAD+ was monitored directly by using lactate dehydrogenase and pyruvate to regenerate NAD+. This rate was sufficiently rapid for the NADH formed from tightly bound NAD+ to be a catalytic intermediate. Although these and other results are consistent with a simple alternating sites model, additional approaches appear necessary to find if subunit catalytic cooperativity occurs with this enzyme.
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PMID:Subunit interaction in catalysis. Some experimental and theoretical approaches with glyceraldehyde-3-phosphate dehydrogenase. 708 42


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