Recent trends in the metabolism and cell biology of vitamin K with special reference to vitamin K cycling and MK-4 biosynthesis.

Abstract

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.

• Authors: Martin J Shearer, Paul Newman
• Journal: Journal of lipid research (J Lipid Res) Vol. 55 Issue 3 Pg. 345-62 (Mar 2014) ISSN: 1539-7262 [Electronic] United States
• PMID: 24489112 (Publication Type: Journal Article, Review)

Chemical References

• Vitamin K 2
• vitamin K1 oxide
• menatetrenone
• Vitamin K 1
• Vitamin K Epoxide Reductases
• Dimethylallyltranstransferase
• UBIAD1 protein, human

Topics

• Animals
• Biosynthetic Pathways
• Diet
• Dimethylallyltranstransferase (metabolism)
• Humans
• Intestinal Mucosa (metabolism)
• Molecular Structure
• Vitamin K 1 (analogs & derivatives, chemistry, metabolism)
• Vitamin K 2 (analogs & derivatives, chemistry, metabolism)
• Vitamin K Epoxide Reductases (metabolism)