Biosynthesis of vitamin B12: does 51-norcobyrinic acid or 151-norcobyrinic acid act as a precursor of cobyrinic acid?
Abstract
51-Norcobyrinic acid and 151-norcobyrinic acid are prepared in labelled form for enzymic experiments that show that neither one acts as a biosynthetic precursor of cobyrinic acid, a late intermediate en route to vitamin B12.