Influence of folic acid on xanthine oxidation in vitro

Abstract

An inverse relationship between liver xanthine oxidase and dietary folic acid has been demonstrated in the chick. Similar effects are reported for D-amino-acid oxidase activity and in glycine metabolism. Since hydrogen peroxide, a product resulting from oxidations involving flavo-protein enzymes, is known to bring about destruction of hæmoglobin, these observations have been interpreted to mean that an excessively rapid rate of such oxidations may contribute to the breakdown of haæmoglobin or hæm-containing enzymes in vivo and thus explain a biochemical change in folic acid deficiency. However, recent reports would suggest that folic acid may not have a direct influence on catalase activity or on liver xanthine oxidase in the rat. Furthermore, earlier observations on the in vitro inhibition by folic acid of xanthopterin oxidase activity have now been ascribed to an aldehyde impurity which is a primary photo-fission product of the vitamin.