Abstract

6-Phosphogluconate dehydrogenase catal)jzes the metal ion-independent oxidative decarboxylation of 6- phosphogluconate (6PG). The enzyme catalyzes a reaction in which 6PG is first oxidized at the 3-position, then decarboxylated to the 1,2-enediol of Ru5P , and then tautomerized to give the Ru5P ketone product. In the reaction, Kl83 acts as a general base, general acid, shuttling a proton between the 3-hydroxyl and itself, and E190 acts as a general acid to protonate C1 of the enediol intermediate in the tautomerization step.