Enzymatic Oxidation of Rifamycins by a Microorganism of the Genus Humicola

概要

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The catalytic properties of partially purified rifamycin oxidase produced intracellularly by a strain of Humicola spp. (ATCC 20620) were investigated. The enzyme was most specific for rifamycin B among the various rifamycin derivatives tested. Its K_m value for this substrate was 0.05 mM. Substrate inhibition was observed at substrate concentrations above 2 mM. Polyol compounds such as p-hydroxy phenoxy acetic acid, p-hydroquinone, and cathecol were moderately oxidized by this enzyme.A pH of 7.8 and a temperature of 45℃ were optimal for the enzyme activity. It was severely inhibited by Fe^<++> and Hg^<++>, but was not affected by other metal ions.As an enzyme source for industrial applications, whole cell preparations of the microorganism were tested. A time lag in the conversion-time profile was observed at the initial stage of the reaction with whole cell enzyme, while no such a trend was detected with acetone-dried whole cells. The cell membrane may exert a diffusional barrier to the molecules of substrate and products. Delipidation of the cell membrane by acetone treatment was therefore advised, especially when a whole cell preparation of the enzyme was to be used for oxidation of rifamycins.
社団法人日本生物工学会の論文
1985-12-25