THE CATABOLISM OF C14-LABELED URACIL, DIHYDROURACIL, AND β-UREIDOPROPIONIC ACID IN RAT LIVER SLICES

Previous work in this laboratory (1) demonstrated the formation of /?-alanine-Cl4 and carbon dioxide-Cl4 from uracil-6-Cl4 in rat liver slices.'The results further indicated that the degradation of P-alanine is the ratelimiting step in the oxidation of carbon atoms 4,5, and 6 of uracil to carbon dioxide.The difficulty in detecting intermediates in the breakdown of uracil to @alanine was ascribed to the rapid and quantitative conversion of dihydrouracil-6-Cl4 to P-alanine.Recently the work of Canellakis (2) demonstrated dihydrouracil (DHU) and p-ureidopropionic acid (BUP) as the intermediates of uracil degradation in the supernatant fluid from rat liver homogenates.The present work describes the further study of the catabolism of uracil in rat liver slices by means of C14-labeled uracil, DHU, BUP, and /3-alanine.The formation of ,&alanine from uracil is demonstrated, and the intermediates DHU and BUP have been identified.The reversibility and rates of degradation of the different steps in this process have been investigated.EXPERIMENTAL