abbr.: MK;
the class name for a series of 2-methyl-3-all-
trans-polyprenyl-1,4-naphthoquinones, also known as vitamins K
2 (see
vitamin K for function). They are antihemorrhagic vitamins, present in bacteria, and possess 1 — 13 prenyl residues, the number of prenyl residues being indicated by a suffixed Arabic number, e.g. menaquinone-6 (MK-6;
also known as farnoquinone). [From methyl naphthaquinone.]