Characterization and Regulatory Properties of Glucose‐6‐Phosphate Dehydrogenase from Black Gram (Phaseolus mungo)

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.