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Purification and structural characterization of water‐soluble menaquinone‐7 produced by Bacillus subtilis natto

2018; Wiley; Volume: 42; Issue: 6 Linguagem: Inglês

10.1111/jfbc.12630

1745-4514

Toshiyuki Chatake, Yasuhide Yanagisawa, Rintaro Inoue, Masaaki Sugiyama, Tatsuhito Matsuo, Satoru Fujiwara, Tadanori Ohsugi, Hiroyuki Sumi,

Vitamin C and Antioxidants Research

Vitamin K is essential for osteogenesis, and vitamin K deficiency causes osteoporosis, leading to hip fracture and coronary disease. Menaquinone-7 (MK-7), one of vitamin K subtypes, is abundantly contained in Japanese traditional fermented food natto. Bacillus subtilis natto secretes a water-soluble macromolecular complex consisting of MK-7 and peptides (natto-MK-7), although MK-7 itself is water-insoluble. However, structural properties of natto-MK-7 have not been well elucidated. In the present study, natto-MK-7 was purified from a liquid culture medium of Bacillus subtilis natto by fast protein liquid chromatography. The protein assay and electrophoresis suggest that natto-MK-7 is a complex composed of three components; menaquinone-7, 10-kDa peptide, and 3-kDa amphiphilic peptides. The hydrodynamic radius of natto-MK-7 determined by the dynamic light scattering experiment suggests that natto-MK-7 has a more compact shape than that predicted in the previous size-exclusion chromatography. Practical applications Japanese traditional fermented food natto contains extremely large amount of menaquinone-7 (natto-MK-7): a subtype of vitamin K2. Actually, Japanese natto eaters get about a half amount of vitamin K required daily from natto, and menaquinone-7 from natto is already on the market. Natto-MK-7 is water-soluble molecular complex, while every type of vitamin K including menaquinone-7 is insoluble to water. This solubility to water is expected to have an advantage in food/medical applications. The present study is the first report of structural analysis of natto-MK-7 by scattering technique. The structural information described in our report can explain how natto-MK-7 acquire a water-solubility, and furthermore, it would be useful for the further improvement of the vitamin K carrier for supplement, pharmaceuticals, and food additives.