Characterization and Regulatory Properties of Glucose-6-Phosphate Dehydrogenase from Black Gram (Phaseolus mungo) |
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| Authors: | HIROSHI ASHIHARA ATSUSHI KOMAMINE |
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| Institution: | Department of Biology, Faculty of Science, Ochanomizu University, Otsuka, Tokyo, 112 Japan;Department of Botany, Faculty of Science, University of Tokyo, Hongo, Tokyo, 113 Japan |
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| Abstract: | Glucose-6-phosphate dehydrogenase (E.C. 1.1.1.49) was partially purified by fractionation with ammonium sulfate and phosphocellulose chromatography. The Km value for glucose-6-phosphate is 1.6 × 10?4 and 6.3 × 10?4M at low (1.0–6.0 × 10?4M) and high (6.0–30.0 × 10?4M) concentrations of the substrate, respectively. The Km value for NADP+ is 1.4 × 10?5M. The enzyme is inhibited by NADPH, 5-phosphoribosyl-1-pyrophosphate, and ATP, and it is activated by Mg2+, and Mn2+. In the presence of NADPH, the plot of activity vs. NADP+ concentration gave a sigmoidal curve. Inhibition of 5-phosphoribosyl-1-pyrophosphate and ATP is reversed by Mg2+ or a high pH. It is suggested that black gram glucose-6-phosphate dehydrogenase is a regulatory enzyme of the pentose phosphate pathway. |
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