Abstract
Potato glucose-6-phosphate dehydrogenase was purified by means of Ca-phosphate gel treatment, (NH4)2SO4 fractionation, DEAE-cellulose column chromatography and Sephadex G-200 column chromatography. The final enzyme preparation had a specific activity of 19 units per mg protein. In the absence of KCl, the optimum pH was 8.0 to 8.5, while in the presence of KCl (0.1M), the optimum pH was not changed but the enzyme activity increased to about 1.5 fold.
Results of product inhibition experiments were consistent with a compulsory ordered mechanism (Ordered Bi Bi type or Theorell Chance type). The Michaelis constant for G-6-P was 3.5×10-4M, and the dissociation constant of enzyme-NADP complex was 1.9×10-5M at optimum condition. The enzyme was inactivated by PCMB, while this inactivation was completely protected by NADP and G-6-P. At high concentration of MgCl2, the inactivation of enzyme by PCMB increased and could not protected by G-6-P.
