REDUCTIVE CATABOLISM OF URACIL AND THYMINE BY BURKHOLDERIA-CEPACIA

Catabolism of uracil and thymine in Burkholderia cepacia ATCC 25416 wa s shown to occur using a reductive pathway. The first pathway enzyme, dihydropyrimidine dehydrogenase, was shown to utilize NADPH as its nic otinamide cofactor. Growth of B. cepacia on pyrimidine bases as the ni trogen source instead of on ammonium sulfate increased dehydrogenase a ctivity at least 32-fold. The second and third reductive pathway enzym es, dihydropyrimidinase and N-carbamoyl-beta-alanine amidohydrolase, r espectively, exhibited activities elevated more than 21-fold when pyri midine or dihydropyrimidine bases served as the nitrogen source rather than ammonium sulfate. The pathway enzyme activities were induced aft er growth on 5-methylcytosine.