The oxidative pathway of carbohydrate metabolism in Escherichia coli. 1. The isolation and properties of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase

Abstract

Glucose 6-phosphate dehydrogenase and phosphogluconate dehydrogenase were separated and partially purified from extracts of Escherichia coli. Opt. conditions for the action of these enzymes in reducing tri-phosphopyridine nucleotide in the presence of their substrates were detd. Both enzymes were activated by bivalent cations as chlorides. Mg++ and Ca++ were most active at about 2 x 10-2 [image]. Michaelis constants for the enzyme-substrate complex were of the order of 3 x 10-4 for glucose 6-phosphate dehydrogenase and 3 x 10-5 for phosphogluconate dehydrogenase. Opt. pH was 7.7-8.6 for glucose 6-phosphate dehydrogenase and 6.6-7.7 for phosphogluconate dehydrogenase, and max. activity of both enzymes occurred at 37[degree].