= Menaquinone-4
<Menaquinone-4> is a member of the <menaquinone> family with four <isoprene>-derived units in its side chain. Its formula is $\mathrm{C_{31}H_{40}O_2}$. The numeral in the name describes the side chain, rather than four molecules of <Vitamin K> or a fourfold concentration.<PubChem Compound database by National Center for Biotechnology Information>[Menatetrenone, CID5282367, formula, structural description and menaquinone-4 synonym]{ref}
In 2010, reducing <UBIAD1> expression in human cells reduced formation of labelled <menaquinone-4> from labelled vitamin-K derivatives. Expressing the candidate enzyme in insect cells supplied complementary evidence, and deuterium <nuclear magnetic resonance> identified the product.<Identification of UBIAD1 as a novel human menaquinone-4 biosynthetic enzyme by Kimie Nakagawa and others>[Abstract, interference, heterologous expression and chemical identification]{ref}
The experiments address different parts of the proposed mechanism. A loss-of-function comparison tests whether a component is required in the original system; expression in another system tests whether it can support the conversion there. Chemical product identification links both results to the named compound. An increase in a generic vitamin-K signal would not establish the same specific biosynthetic claim.
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