Takeshi Takahashi, H. Yamashita, E. Kato
1976
Citations
2
Influential Citations
17
Citations
Journal
Agricultural and biological chemistry
Abstract
D-Glucono-γ-lactone dehydrogenase is an enzyme dehydrogenating D-glucono-γ-lactone to D-erythorbic acid (D-araboascorbic acid, isovitamin C). D-Erythorbic acid was obtained as a cultural metabolite of penicillia. The enzyme of P. notatum was so labile that detailed studies were difficult. The enzyme of P. cyaneo-fulvum was relatively stable, however, and could be purified about 100-fold in specific activity to give a single protein. The enzyme has similar properties to L-gulono-γ-lactone oxidase (EC 1. 1. 3. 8), an L-ascorbic acid producing enzyme in animals, and to L-galactone-γ-lactone dehydrogenase (EC 1. 3. 2. 3), an L-ascorbic acid producing enzyme in plants. Molecular weight estimated by gel filtration is about 150, 000. The substrate of the enzyme seemed to be only D-glucono-γ-lactone. Km value for the substrate was 1.7±0.2×10-3M. Fe3+, Fe2+, Cu2+, Hg2+ and Ag+ inhibited the enzyme activity, but PCMB did not. Opt. pH for the enzyme reaction was 5.6_??_6.0, and the activity was completely lost on keeping at 55°C for 30min at the opt. pH. The prosthetic group seemed to be a flavin, but was difficult to identify by normal procedures. It is considered that the prosthetic group is a flavin covalently bound to the enzyme protein, as in L-gulono-γ-lactone oxidase. Phenazine methosulfate and dichlorophenolindophenol acted as a role as hydrogen acceptors, although their activity was very low compared with free oxygen. It is considered that this enzyme is a “dehydrogenase.”