抄録
5KGlcA reductase which catalyses the reaction,
GLcA+NADP+_??_5KGlcA+NADPH+H+,
was partially purified from the soluble fraction of Acetobacter suboxydans. The enzyme was found to have an optimum pH of about 7.5 in the forward reaction (G1cA→5KG1cA) and that of about 9.5 in the reverse reaction. NADP was three times as effective as NAD. Mannoic and idonic acids in addition to gluconic acid were shown to be oxidized at a detectable rate. Examination of the reaction product proved that 5KGlcA and gluco-nic acid were produced in the forward and reverse reactions, respectively. The equilibrium studies revealed that this reaction is very unfavorable with respect to the forma-tion of 5KGlcA. (K=3.5×lO-12M). Some physiological significances of the enzyme in the formation of 5KGIcA are discussed.
The author wishes to express his thanks to Professor S. Tanaka for his interest and encouragement. Thanks are also due to Dr. Y. Nozaki for his kind supply of 2KGIcA and idonic acid.
