The nonenzymatic decomposition of 5-methylbarbituric acid.

Studies with Mycobacterium and Corynebacterium, which metabolize pyrimidines via the oxidative pathway (l-5), have revealed that the first product of thymine catabolism is 5-methylbarbituric acid. The metabolic fate of 5-methylbarbituric acid remains to be elucidated. Work in this laboratory has shown that 5-methylbarbituric acid supports growth of Corynebacterium and is rapidly metabolized by resting cells. When this compound was incubated with cell-free extracts of the same organism, it was found to disappear slowly from the reaction media. However similar results were obtained in control experiments, indicating a nonenzymatic degradation. It has been reported previously that 5-methylbarbituric acid is spontaneously oxidized to 5-hydroxy-5-methylbarbituric acid (1, 6). Further investigation of this decomposition has shown that the latter compound is also unstable and undergoes further decomposition under mild conditions to yield several products. These decomposition products were possible intermediates in the catabolism of 5-methylbarbituric acid, and they were isolated, identified, and prepared for use as substrates. Two of the products characterized in this paper are methyltartronylurea and lactylurea, compounds that apparently have not been previously described.