ON THE DECOMPOSITION OF PYRIMIDINES BY BACTERIA II

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Abstract
Enzyme prepns. of Nocardia corallina can be obtained by extracting alumina-ground cells. The activity of these extracts against thymine and uracil can be demonstrated only in the presence of methylene blue. Under these conditions thymine and uracil are oxidized to substances having the overall composition of 5-methyl-barbituric acid and barbituric acid, respectively. The results of expts. indicate that the demethyla-tion of thymine normally does not proceed under the exptl. conditions. Thus, it appears that uracil is not a normal intermediate in the decomposition of thymine. Barbituric acid is hydrolyzed by the enzyme prepn. with the formation of 1 mole of CO2, 2 moles of NH3, and 1 mole of malonic acid per mole of substrate used. These data offer strong evidence for the following pathway of thymine and uracil degradation:.[image].Cell free extracts of N. corallina active on thymine, uracil, and barbituric acid have been obtained only from cells grown in thymine, uracil and barbituric acid; enzyme prepns. from glucose grown cells are devoid of such activity.

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