Transient kinetic studies of the reversible oxidative phosphorylation of d-glyceraldehyde 3-phosphate catalysed by d-glyceraldehyde 3-phosphate dehydrogenase show that all four sites of the tetrameric lobster enzyme are simultaneously active, apparently with equal reactivity. The rate-determining step of the oxidative phosphorylation is NADH release at high pH and phosphorolysis of the acyl-enzyme at low pH. For the reverse reaction the rate-determining step is a process associated with NADH binding, probably a conformation change, at high pH and d-glyceraldehyde 3-phosphate release at low pH. NADH has previously been shown to be a competitive inhibitor of the enzyme with respect to d-glyceraldehyde 3-phosphate and vice versa. This is consistent with the mechanism deduced from transient experiments given the additional proviso that 1-arseno-3-phosphoglycerate has a half-life of about 1min or longer at pH7. The dissociation constants of d-glyceraldehyde 3-phosphate and 1,3-diphosphoglycerate to the NAD+-bound enzyme are too large to measure but are nevertheless consistent with the low Km values of these substrates.
Research Article| March 01 1971
Rate-determining processes and the number of simultaneously active sites of d-glyceraldehyde 3-phosphate dehydrogenase
Biochem J (1971) 122 (1): 71–77.
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D. R. Trentham; Rate-determining processes and the number of simultaneously active sites of d-glyceraldehyde 3-phosphate dehydrogenase. Biochem J 1 March 1971; 122 (1): 71–77. doi: https://doi.org/10.1042/bj1220071
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