Modification of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides with the 2',3'-dialdehyde derivative of NADP+ (oNADP+).
Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides is irreversibly inactivated by the 2,3'-dialdehyde of NADP+ (oNADP+) in the absence of substrate. The inactivation is first order with respect to NADP+ concentration and follows saturation kinetics, indicating that the enzyme initially forms a reversible complex with the inhibitor followed by covalent modification (KI = 1.8 mM). NADP+ and NAD+ protect the enzyme from inactivation by oNADP+. The pK of inactivation is 8.1. oNADP+ is an effective coenzyme in assays of glucose-6-phosphate dehydrogenase (Km = 200 microM). Kinetic evidence and binding studies with [14C] oNADP+ indicate that one molecule of oNADP+ binds per subunit of glucose-6-phosphate dehydrogenase when the enzyme is completely inactivated. The interaction between oNADP+ and the enzyme does not generate a Schiff's base, or a conjugated Schiff's base, but the data are consistent with the formation of a dihydroxymorpholino derivative.[1]References
- Modification of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides with the 2',3'-dialdehyde derivative of NADP+ (oNADP+). White, B.J., Levy, H.R. J. Biol. Chem. (1987) [Pubmed]
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