The kinetics of the reaction of d-glyceraldehyde 3-phosphate dehydrogenase with 5,5′-dithiobis-(2-nitrobenzoic acid) show that NAD% dissociates from the enzyme before the reaction. In contrast 2-chloromercuri-4-nitrophenol reacts with the holoenzyme without prior dissociation of NAD%. These studies and observations on the dissociation constant of NAD% to the lobster enzyme show that NAD% must dissociate from sites modified by substrates during the reductive dephosphorylation of 1,3-diphosphoglycerate. All four sites per tetramer of the apoenzyme are acylated by 1,3-diphosphoglycerate. Hydrolysis of the acyl-enzyme occurs at a significant rate even in the absence of NAD%, which may explain previous estimates that only two sites per tetramer can readily be acylated.
Research Article|September 01 1971
Reactions of d-glyceraldehyde 3-phosphate dehydrogenase with chromophoric thiol reagents
P. J. Harrigan;
Biochem J (1971) 124 (3): 573-580.
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P. J. Harrigan, D. R. Trentham; Reactions of d-glyceraldehyde 3-phosphate dehydrogenase with chromophoric thiol reagents. Biochem J 1 September 1971; 124 (3): 573–580. doi: https://doi.org/10.1042/bj1240573
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