Carbohydrate Oxidation by Pseudomonas Ruorescens

Glucose utilization by extracts of Pseudomonas jhwrescens involves its oxidation to gluconate and 2-ketogluconate (1, 2) by cytochrome-linked dehydrogenases (1). 2-Ketogluconate is phosphorylated by an inducible kinase, which is distinct from gluconokinase, and 2-keto-6-phosphogluconate, the phosphorylation product, has been isolated and identified (3). The conversion of 2-keto-6-phosphogluconate to 2 moles of pyruvate by the crude extract also has been demonstrated (3). Preliminary experiments showed that pyruvate produced from 2-ketogluconateCi4 was labeled qualitatively as though derived via the Entner-Doudoroff reactions involving dehydration of 6phosphogluconate and cleavage of 2-keto-3-deoxy-6-phosphogluconate; that is, the pyruvates from 2-ketogluconate-l-Cl4 and -6-Cl4 were carboxyland methyl-labeled, respectively (4). In this connection, 6-phosphogluconate dehydrase and 2-keto-3deoxy-6-phosphogluconate aldolase have been purified from P. jzwrescens and their properties documented (5, 6). The phosphorylation of 2-ketogluconate has been found in many organisms grown on 2-ketogluconate, including Aerobacter cloacae (7), Aerobacter aerogenes (8), Leuconostoc mesenteroides (9, and others (10). 2-Keto-6-phosphogluconate has been isolated and characterized by DeLey (11). 2-Keto-6-phosphogluconate reduction to 6-phosphogluconate by a pyridine nucleotide-requiring dehydrogenase and the further conversion to pentose phosphate and COZ also have been established (12). The 2keto-6-phosphogluconate reductase was 20 times more active with reduced triphosphopyridine nucleotide than with reduced diphosphopyridine nucleotide. The discovery of 2-keto-6-phosphogluconate reductase has facilitated a formulation of the reaction sequence for 2-ketogluconate utilization in both L. mesenteroides and P. $uorescens. This paper reports the evidence for a pathway of 2-keto-6-phosphogluconate utilization in P. jluorescens as shown in Fig. 1.