納豆中の水可溶性ビタミンK_2複合体について

概要

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We have previously shown that Bacillus subtilis secreted menaquinone-7 into the incubation medium as a water soluble complex with a glycopeptide which was named vitamin-K_2-binding factor, KBF(Eur. J.Biochem., 192, 219-224,1990). Here we examined the gross properties of KBF found in natto which are boiled soybeans fermented by Bacillus natto, a different strain of B. subtilis. Most vitamin K_2 of natto synthesized by B. natto was found in the water extract whereas vitamin K_2 known to be contained in soybean itself was only water-washed natto, indicating that KBF in natto is responsible for solubilization of vitamin K_2. The elution profiles of the water extract by DEAE-chromatography and Sepharose 4B chromatography were similar to those obtained with KBF of B. subtilis, revealing that KBF in natto is acidic substance with apparent molecular mass of 100 kD. Examination of partially purified KBF by polyacrylamide gel disc electrophoresis showed that KBF is a glycopeptides stainable with both Coomassie brilliant blue and periodic acid/Schiff reagent and that vitamin K_2 was comigrated with KBF as a broad band. As vitamin K_2 of water soluble form rapidly decreased upon storage of natto, the stability of KBF was also examined under various storage conditions.
社団法人日本家政学会の論文
1992-07-15