The Mechanism of Reaction of Cys- 149 of D-Glyceraldehyde-3-phosphate Dehydrogenase with p-Hydroxy-mercuribenzoate

Batke, József and Keleti, Tamás and Fischer, E. (1974) The Mechanism of Reaction of Cys- 149 of D-Glyceraldehyde-3-phosphate Dehydrogenase with p-Hydroxy-mercuribenzoate. EUROPEAN JOURNAL OF BIOCHEMISTRY, 46 (2). pp. 307-315. ISSN 0014-2956

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Abstract

1. During the reaction of the Cys-149 residue of pig muscle ~-glyceraldehyde-3-phosphate dehydrogenase holoenzyme with p-hydroxymercuribenzoate a ternary complex is first formed. The process follows second-order kinetics as measured by the disappearance of the absorption band at 360 nm characteristic of the enzyme-coenzyme charge-transfer interaction. Mercaptide bond formation takes place in this ternary complex as a first-order intramolecular transformation. The firmly bound coenzyme molecules are also released in a first-order reaction, as detected by the disappearance of the absorption band at 272 nm characteristic of the enzyme-coenzyme complex, simultaneously with the formation of mercaptide bond. 2. Both the formation of mercaptide bond and the release of NAD show biphasic first-order kinetics, which indicates that there are differences in the reactivities of Cys-149 residues and between the coenzyme binding sites within the tetramer. The biphasic first-order kinetics of mercaptide bond formation was also observed in the reaction of the apoenzyme with p-hydroxymercuribenzoate.

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