UBIAD1 is a membrane-associated prenyltransferase with a demonstrated role in making menaquinone-4, a Vitamin K form. It attaches an isoprene-derived side chain to a suitable precursor, including menadione. It should be distinguished from menaquinone-4, the small molecule produced by the reaction.[ref]
In 2010, siRNA-mediated reduction of UBIAD1 in human cells decreased labelled-product formation. Expressing UBIAD1 in insect cells enabled production of labelled menaquinone-4, whose structure was checked using deuterium nuclear magnetic resonance.[ref]
Identification of UBIAD1 as a novel human menaquinone-4 biosynthetic enzyme by Kimie Nakagawa and others. Abstract and Figures2–3
Loss-of-function and gain-of-function comparisons thus connected a particular protein to a defined chemical transformation; neither expression alone nor a fluorescent localization image would establish that transformation. New to topics? Read the docs here!