The formation of menaquinone-4 (vitamin K) and its oxide in some marine invertebrates.

Three echinoderms, a crustacean, a mollusc and a coelenterate were injected with either [2-14C]mevalonate and unlabelled menadione (2-methyl-1,4-naphthaquinone) or 2-[14C]methyl-1,4-naphthaquinone. In each case the label was incorporated into menaquinone-4.[2-14C]Mevalonate was incorporated into menaquinone-4 in the crab (Carcinus maenas) only in the presence of menadione, the organism presumably being unable to synthesize the naphthaquinone nucleus. The starfish Asterias rubens and C. maenas incorporated the label into a compound which was identified chromatographically as 2,3-epoxymenaquinone-4. The significance of menaquinone-4 and these animals is discussed.