A New Phosphorylated Intermediate in Glucose Oxidation

A new biochemical pathway for the oxidative metabolism of glucose has recently been described in Pseudomonas saccharophila (1).It involves the phosphorylation and oxidation of glucose to 6-phosphogluconic acid and the subsequent enzymatic split of 6-phosphogluconic acid with formation of pyruvic acid and n-glyceraldehyde-3-phosphate in stoichiometric amounts.A similar mechanism has since been found in Pseudomonas jluorescens (2).The hypothesis was advanced (1) that 6-phosphogluconic acid might undergo an enzymatic dehydration and rearrangement to 2-keto-3-deoxy-Gphosphogluconic acid, which would then be split by a modified aldolase reaction analogous to that described by Racker for the synthesis of deoxyribose phosphate (3).Two enzymatic activities have been separated from cell-free extracts of P. saccharophila.Phosphogluconic dehydrase converts G-phosphogluconic acid to a phosphorylated keto acid, but does not further attack this compound.The splitting enzyme has no effect on 6-phosphogluconic acid, but rapidly splits the keto acid to pyruvic acid and n-glyceraldehyde-3-phosphate.The preparation and properties of the new intermediate compound, which appears to be 2-keto-3-deoxy-6-phosphogluconic acid, will be described in the present paper.