Biosynthesis of uridine monophosphate in Plasmodium berghei.

High activities of the enzymes orotate phosphoribosyltransferase and orotidylate decarboxylase, that convert orotic acid to uridine monophosphate, have been demonstrated in crude supernatants obtained from lysed Plasmodium berghei. The enzymes are inhibited in vitro by 5-azaorotate, 5-azauracil and 6-azauracil. Of these, 5-azaorotate was the most effective and could serve as the prototype of a potential antimalarial.