An alternative pathway for 3-phosphoglycerate generation in Veillonella

Abstract

Previous investigations have shown that members of the genus Veillonella possess the enzymes for a reversed glycolytic pathway of gluconeogenesis. Enzymatic and radioisotopic analysis of transformations occurring among C2 and C3 fragments in lactate-grown Veillonella alcalescens cell extracts revealed evidence for a second, novel mode of 3-phosphoglycerate biosynthesis involving the intermediates glyoxylate and glycerate. In this alternative pathway, malate is first cleaved in the presence of ATP by the action of a malate-ATP lyase to yield glyoxylate. Glyoxylate carboligase catalyzed the condensation of two molecules of glyoxylate to form CO2 and a C3 intermediate tentatively identified as hydroxypyruvate. Hydroxypyruvate is reduced to glycerate in the presence of NADH or NADPH by glycerate dehydrogenase. A glycerate kinase was purified 168-fold and shown to catalyze the ATP-dependent phosphorylation of glycerate to 3-phosphoglycerate. Glyoxylate reductase activity which could utilize NADH or NADPH as electron donors was also detectable.