YAKUGAKU ZASSHI
Online ISSN : 1347-5231
Print ISSN : 0031-6903
ISSN-L : 0031-6903
誌上シンポジウム
ビタミンKの生体内活性化とその意義
中川 公恵
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ジャーナル フリー

2013 年 133 巻 12 号 p. 1337-1341

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  Natural vitamin K is found in two forms: a plant form, phylloquinone (PK) and bacterial forms, menaquinones (MKs). PK is a major form of dietary vitamin K; however, the most prevalent form of vitamin K in animals and humans is menaquinone-4 (MK-4). Despite its high concentrations, the origin of MK-4 is yet to be defined. It is postulated that PK is converted into MK-4 and accumulates in extrahepatic tissues. The molecular mechanisms for these conversion reactions have been unclear. To identify the MK-4 biosynthetic enzyme, we screened the human genome database for prenylation enzyme. We found UbiA prenyltransferase domain containing 1 (UBIAD1), a human homologue of Escherichia coli prenyltransferase menA. The short interfering RNA against the UBIAD1 gene inhibited the conversion of deuterium-labelled vitamin K derivatives into deuterium-labelled-MK-4 (MK-4-d7) in human cells. We confirmed that the UBIAD1 gene encodes an MK-4 biosynthetic enzyme through its expression and conversion of deuterium-labelled vitamin K derivatives into MK-4-d7 in insect cells infected with UBIAD1 baculovirus. UBIAD1 was localized in endoplasmic reticulum. Our results show that UBIAD1 is a human MK-4 biosynthetic enzyme. This identification will permit more effective decisions to be made about vitamin K intake and bone health.

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© 2013 by the PHARMACEUTICAL SOCIETY OF JAPAN
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