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标题：Recent trends in the metabolism and cell biology of vitamin K with special reference to vitamin K cycling and MK-4 biosynthesis
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作者：Martin J. Shearer ; Paul Newman
期刊名称：JLR Papers In Press
印刷版ISSN：0022-2275
电子版ISSN：1539-7262
出版年度：2014
卷号：55
期号：3
页码：345-362
DOI：10.1194/jlr.R045559
语种：English
出版社：American Society for Biochemistry and Molecular Biology
摘要：In contrast to other fat-soluble vitamins, dietary vitamin K is rapidly lost to the body resulting in comparatively low tissue stores. Deficiency is kept at bay by the ubiquity of vitamin K in the diet, synthesis by gut microflora in some species, and relatively low vitamin K cofactor requirements for γ-glutamyl carboxylation. However, as shown by fatal neonatal bleeding in mice that lack vitamin K epoxide reductase (VKOR), the low requirements are dependent on the ability of animals to regenerate vitamin K from its epoxide metabolite via the vitamin K cycle. The identification of the genes encoding VKOR and its paralog VKOR-like 1 (VKORL1) has accelerated understanding of the enzymology of this salvage pathway. In parallel, a novel human enzyme that participates in the cellular conversion of phylloquinone to menaquinone (MK)-4 was identified as UbiA prenyltransferase-containing domain 1 (UBIAD1). Recent studies suggest that side-chain cleavage of oral phylloquinone occurs in the intestine, and that menadione is a circulating precursor of tissue MK-4. The mechanisms and functions of vitamin K recycling and MK-4 synthesis have dominated advances made in vitamin K biochemistry over the last five years and, after a brief overview of general metabolism, are the main focuses of this review.
关键词：phylloquinone ; menaquinones ; vitamin K epoxide ; γ-carboxyglutamate proteins ; vitamin K antagonists ; anticoagulants ; warfarin ; warfarin resistance ; vitamin K epoxide reductase ; vitamin K dehydrogenase ; UbiA prenyltransferase-containing domain 1