1887

Abstract

The phototrophic bacterium strain Si4 induced ribitol dehydrogenase (EC 1.1.1.56) when grown on ribitol- or xylitol-containing medium. This ribitol dehydrogenase was purified to apparent homogeneity by ammonium sulphate precipitation, affinity chromatography on Procion red, and chromatography on Q-Sepharose. For the native enzyme an isoelectric point of pH 6·1 and an apparent of 50000 was determined. SDS-PAGE yielded a single peptide band of 25000 suggesting a dimeric enzyme structure. The ribitol dehydrogenase was specific for NAD but unspecific as to its polyol substrate. In order of decreasing activity ribitol, xylitol, erythritol, D-glucitol and D-arabitol were oxidized. The pH optimum of substrate oxidation was 10, and that of substrate reduction was 6·5. The equilibrium constant of the interconversion of ribitol to D-ribulose was determined to be 0·33 nM at pH 7·0 and 25 °C. The -values determined for ribitol, ribulose, xylitol and NAD (in the presence of ribitol) were 6·3, 12·5, 77 and 0·077 mM, respectively. Because of the favourable for ribitol, a method for quantitative ribitol determination was elaborated.

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/content/journal/micro/10.1099/00221287-138-6-1277
1992-06-01
2019-11-15
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http://instance.metastore.ingenta.com/content/journal/micro/10.1099/00221287-138-6-1277
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