Properties of phosphogluconate dehydrogenases isolated from the liver of carp, grass carp, rainbow trout, eel, and yellowtail were investigated. On DEAE-cellulose column chromatography, the isolate of each species produced a single peak of enzyme activity. The molecular weight of the enzyme was estimated to be about 100, 000, and the optimum pH was found to be between 8.0-8.3. The enzyme was highly specific for NADP and 6-phosphogluconate for which Km values were 4.4-2.7, μM and 21-58 μM , respectively. From these results, the enzyme was considered to be phosphogluconate dehydrogenase (decarboxylating) (EC 1.1.1.41).
Mg2+ and ATP inhibited the enzyme activity, while dehydroisoandrosterone had no effect at all. There were no marked differences among the properties of the enzymes from different species.