Chemical Classification and Structure
Menaquinone (MK) is the scientific name for vitamin K2, distinguishing it from vitamin K1 (phylloquinone). 1, 3
Menaquinones exist as a family of compounds designated MK-2 through MK-14, based on the length of their isoprenoid side chain. 4
The structural difference between vitamin K1 and K2 lies in their side chains, which affects their absorption rates, tissue distribution, and bioavailability. 5
Biological Sources and Synthesis
Intestinal bacteria, including E. coli, synthesize vitamin K2 (menaquinone) but not K1, contributing to meeting vitamin K requirements. 1
Menaquinone is a lipid-soluble molecule that participates in bacterial electron transport chains and serves as an essential vitamin in mammalian cells for activating proteins involved in blood clotting and bone metabolism. 2
Clinical Relevance
Dietary intake of menaquinones accounts for up to 25% of total vitamin K intake and contributes to the biological functions of vitamin K. 3
Vitamin K2 (MK-7 form) has been shown to be bioactive in regulating osteoporosis, atherosclerosis, cancer, and inflammatory diseases without risk of negative side effects or overdosing. 5
Current dietary reference values for vitamin K are based exclusively on phylloquinone (K1), despite menaquinones having distinct pharmacokinetic properties and potentially different health impacts. 3