抄録
5-Ketofructose reductase [D-fructose: NADP oxidoreductase, EC class 1. 1. 1], an enzyme catalyzing the reduction of 5-keto-D-fructose to D-fructose in the presence of NADPH, was purified about 200-fold from the soluble fraction of Gluconobacter albidus. The enzyme seems to be a typical “reductase, ” because it was active only for reduction, and the reaction was scarcely reversible. NADH was by far less effective than NADPH as hydrogen donor. The optimal pH was 7.0. Km value for 5-keto-D-fructose and NADPH were approximately 6.7×10-3 M and 1×10-5 M, respectively. The enzyme was strongly inhibited by p-chloro-mercuribenzoate and phenylmercuric nitrate. An energy for activation of about 5, 500 cal./mole was determined for the reduction of 5-keto-D-fructose. The role of this enzyme was discussed in connection with fructose catabolism in Gluconobacter species.
