Metabolic conversion of orotic acid hydrazide into a nucleotide in mouse and rat liver.

When [2-14C] orotic acid hydrazide (OAH) was injected i.p. in mice the bulk of the radioactivity of the acid-soluble fraction of liver was found in a metabolite obviously not identical with natural pyrimidines known so far as elucidated by chromatographic methods. This compound is also formed in vitro by the cytosolic fraction of mouse liver or by purified orotate phosphoribosyltransferase/orotidine-5'-phosphate decarboxylase (OPRTase/ODCase) provided that PRPP is present in the medium. Using alkaline hydrolysis and snake venom to split off the hydrazine- and the phosphate group, respectively, the metabolic product of OAH was identified as a nucleotide, orotic acid hydrazide nucleoside monophosphate. The identity of OMP and orotidine thus formed was confirmed by thin-layer chromatography.