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. 1985 Apr 1;227(1):305–310. doi: 10.1042/bj2270305

Half-site reactivity in 6-phosphogluconate dehydrogenase from human erythrocytes.

F Dallocchio, M Matteuzzi, T Bellini
PMCID: PMC1144840  PMID: 3994686

Abstract

6-Phosphogluconate dehydrogenase from human erythrocytes was purified by an improved procedure. Binding studies showed that the dimeric enzyme binds 2 mol of NADP+/mol but only 1 mol of NADPH/mol, and that the bindings of oxidized and reduced coenzyme are mutually exclusive. From initial-rate kinetics and inhibition studies, a sequential random-order mechanism is proposed. Double-reciprocal plots with NADP+ as varied substrate show a downward curvature, indicating a negative co-operativity. We suggest that the negative co-operativity observed kinetically is a result of the half-site reactivity for the NADPH. The different binding stoichiometries for NADP+ and NADPH generate a non-linear relationship between the apparent dissociation constant for the NADPH and the concentrations of the NADP+, resulting in a regulatory mechanism highly sensitive to the changes in the NADP+/NADPH ratio.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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