Enzymatic Studies on the Oxidation of Sugar and Sugar Alcohol:VIII. Particle-bound L-Sorbose Dehydrogenase from <i>Gluconobacter suboxydans</i>

J-STAGE
  • SATO KIYOSHI
    Institute of Applied Microbiology, University of Tokyo
  • YAMADA YUZO
    Institute of Applied Microbiology, University of Tokyo
  • AIDA KÔ
    Institute of Applied Microbiology, University of Tokyo
  • UEMURA TEIJIRO
    Institute of Applied Microbiology, University of Tokyo

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説明

An L-sorbose-dehydrogenating enzyme was found in a particulate fraction of Gluconobacter suboxydans grown on a sorbitol medium. The reaction with 2, 6-dichlorophenol indophenol as acceptor was formulated as; L-sorbose+acceptor→5-keto-D-fructose+ reduced acceptor. The optimal pH for the activity was 6.4. Km value for L-sorbose was calculated as 4.3×lO-3M. p-Chloromercuribenzoate, phenylmercuric nitrate, Ag+, Hg2+, and Cu2+ inhibited the enzyme activity to considerable degrees. D-Fructose, sucrose, and dulcitol were inactive as substrate. The enzyme preparation had the activity toward aldoses, D-gluconate, 2-keto-n-gluconate, and polyols. It was, however, proved that the L-sorbose-dehydrogenating activity was due to a separate enzyme other than glucose dehydrogenase, gluconate dehydrogenase [EC 1. 1. 99. 3], ketogluconate dehydrogenase [EC 1. 1. 99. 4], and mannitol dehydrogenase [EC 1. 1. 2. 2]. Thus, this enzyme, to which the rule of Bertrand-Hudson is not applicable, was proposed as a new type of "ketose dehydrogenase".

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