PURIFICATION AND CHARACTERIZATION OF OYSTER GLUCOSE-6-PHOSPHATE-DEHYDROGENASE

Glucose 6-phosphate dehydrogenase, (EC 1.1.1.49; Glc-6-P DH) in oyster Crassostrea gigas was extracted with 10 mm Tris-HCI buffer solution and purified by ammonium sulfate fractionation, Sepharose 6B gel filtration, and DEAE-Sephadex A-50, and CM-Sepharose CL-6B chromatography. A single fraction exhibiting Glc-6-P DH activity was obtained by CM-Sepharose CL-6B chromatography. The purified Glc-6-P DH was electrophoretically homogenous. The optimal pH for hydrolysis of Glc-6-P was 8. The temperature which inactivated 50% of enzyme was 47-degrees-C in 15-min treatment. The molecular weight was 204,000. Beyond 35-degrees-C the activation energy of Glc-6-P DH was 5,400 cal/mol, and below 35-degrees-C it was 10,900 cal/mol. The enzyme was inhibited by Zn2+ and Hg2+ ions in low concentration and by Co2+ and Cu2+ ions in high concentration. However, it can be activated by adding Ca2+, Mg2+, and Mn2+ ions in high concentration.