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Abstract
Pyrimidine base catabolism in Pseudomonas stutzeri ATCC 17588 was investigated and was found to occur by means of the reductive pathway. Pyrimidine bases and their respective reductive pathway catabolic products could serve as nitrogen sources for growth of P. stutzeri. Activities of the three enzymes associated with the reductive pathway of pyrimidine catabolism were detected in cells of P. stutzeri. The initial enzyme of the reductive pathway, dihydropyrimidine dehydrogenase, utilized NADH as its nicotinamide cofactor. Cells grown on pyrimidine bases as nitrogen sources contained elevated dehydrogenase activity relative to those grown on ammonium sulphate as nitrogen source. Activities of the second and third reductive pathway enzymes, dihydropyrimidinase and N-carbamoyl-β-alanine amidohydrolase, respectively, were also affected by growth conditions. If pyrimidine or dihydropyrimidine bases served as nitrogen sources, increases in the levels of these enzymes were observed compared to their activities determined when the nitrogen source was ammonium sulphate.
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