6-Phosphogluconate dehydrogenase from leuconostoc mesenteroides.

The pathways for degradation of 6-phosphogluconate have been rather clearly defined for several organisms, the most notable of which are yeast (Horecker, 1953), Escherichia coli (Cohen, 1951), Pseudomonas saccharophila (Entner and Doudoroff, 1952; MacGee and Doudoroff, 1954), and Pseudomonas fluorescens (Kovachevich and Wood, 1954). The enzymes from yeast and E. coli appear to be similar, if not identical, in that 6-phosphogluconate is dehydrogenated and decarboxylated to yield ribulose-5-phosphate. The keto-pentose phosphate is in equilibrium with ribose-5-phosphate. P. saccharophila and P. fluorescens, on the other hand, dehydrate and cleave 6-phosphogluconate to yield one molecule each of pyruvate and glyceraldehyde-3-phosphate. Enzymatic (DeMoss et al., 1951, 1953) and isotopic studies (Gunsalus and Gibbs, 1952) have indicated the presence in Leuconostoc mesenteroides of an anaerobic hexosemonophosphate pathway, the exact nature of which has yet to be demonstrated. The most likely pathway, as deduced from the reports quoted, is similar to that of yeast and E. coli. In the present report, studies on the purification and properties of a 6-phosphogluconate dehydrogenase from L. mesenteroides are described. The results obtained tend to support the concept of similarity of the yeast, E. coli, and L. mesenteroides pathways.