Menaquinone 4-d7 (MK-4-d7) is intended for use as an internal standard for the quantification of MK-4 by GC- or LC-MS. MK-4 is the predominant homolog of vitamin K2 and is composed of a naphthoquinone base with four isoprenoid units in the side chain.1 It is formed primarily via conversion of vitamin K1 in vivo and accumulates in various tissues, including the brain.2,3 MK-4 halts the cell cycle at the G1 phase in HepG2, Hep3B, and Huh7 hepatocellular carcinoma cells in a concentration-dependent manner.4 It also inhibits IκB kinase (IKK) activity, IκBα phosphorylation, and the transcriptional activity of NF-κB. Vitamin K2 may have a role in bone metabolism.1
1.Plaza, S.M., and Lamson, D.W.Vitamin K2 in bone metabolism and osteoporosisAltern. Med. Rev.10(1)24-35(2005) 2.Shearer, M.J., and Newman, P.Metabolism and cell biology of vitamin KThromb. Haemost.100(4)530-547(2008) 3.Okano, T., Shimomura, Y., Yamane, M., et al.Conversion of phylloquinone (vitamin K1) into menaquinone-4 (vitamin K2) in mice: Two possible routes for menaquinone-4 accumulation in cerebra of miceJ. Biol. Chem.283(17)11270-11279(2008) 4.Ozaki, I., Zhang, H., Mizuta, T., et al.Menatetrenone, a vitamin K2 analogue, inhibits hepatocellular carcinoma cell growth by suppressing cyclin D1 expression through inhibition of nuclear factor κB activationClin. Cancer Res.13(7)2236-2245(2007)