CATABOLISM OF PTERIDINE COFACTORS .I. PROPERTIES AND METABOLISM IN RAT LIVER HOMOGENATES OF TETRAHYDROBIOPTERIN AND TETRAHYDRONEOPTERIN

The stability of tetrahydropterins to oxidation has been investigated. Oxidation products, pterin and dihydroxanthopterin, of tetrahydrobiopterin were separated and identified. The cleavage of the side chain of tetrahydroneopterin is shown to be an irreversible reaction coupled to an oxidative process. The side chain is split off as glyceraldehyde. Incubation mixtures of labeled tetrahydrobiopterin in rat liver homogenates have been analyzed using chromatographic procedures, whic allow the balances of all pteridine metabolites to be established. Formation of the acidic products, lumazine, 6-hydroxylumazine and 6,7-dihydroxylumazine, from tetrahydrobiopterin in these homogenates is ascribed to enzymatic reactions which are characterized under various conditions. The occurrence of some pteridines usually present in biological extracts is discussed in the light of these findings. © 1969.