6-Phosphogluconate dehydrogenase from Drosophila melanogaster: Physical and kinetic properties in comparison with the yeast enzyme

Abstract

1. 1. 6-phosphogluconate dehydrogenase from Drosophila melanogaster and from Candida utilis were compared with respect to their native and subunit molecular weights, pH optimum, temperature optimum, thermal stability and kinetic properties. 2. 2. The two enzymes have similar native molecular weights. However, SDS-acrylamide gel electrophoresis indicates subunits of 53,400 for yeast 6PGD but dissimilar subunits of 54,800 and 53,300 for Drosophila 6PGD. 3. 3. The yeast and Drosophila enzymes exhibit similar pH optima and have similar E a and Q 10 values. 4. 4. For the oxidative decarboxylation of 6-phosphogluconate the K m values for 6PG and NADP + are similar for both the yeast and Drosophila enzymes. 5. 5. Both enzymes are competitively inhibited by F-1, 6-diP with respect to 6PG and with NADPH for NADP +, the yeast enzyme being more sensitive to both inhibitors. Mixed inhibition with respect to 6PG was observed with Ru-5-P.