Distribution of quinolinate phosphoribosyl-transferase in animals, plants and microorganisms.

Abstract

Distribution of quinolinate phosphoribosyltransferase (an intermediary enzyme of NAD de novo biosynthesis) in animals, plants and microorgan-isms were investigated by radioassay using quinolinic acid-2, 3, 7, 8-14C as substrate. The enzyme activity was found to be widely distributed in nature. High activities were observed in rat liver, persimmon leaf, cucumber, Shiitake mushroom, Enokitake mushroom, baker's yeast, Pseudomonas riboflavina and Neurospora crassa. In mammals, signi-ficantly high activity was found in liver and kidney, but some activities were detected in brain and spleen. In some of fish livers, plants and microorganisms, the enzyme activity was not detected. The results suggest the possibility that another de novo biosynthetic pathway of NAD, which does not pass through quinolinic acid as an intermediate, may exist in those organisms.