Synthesis of thymidine nucleotides in Bacillus subtilis

To investigate the synthesis of thymidine nucleotides in Bacillus subtilis, mutants that carried various combinations of thyA, thyB, and other mutations affecting pyrimidine metabolism were isolated. It was found that exogenously supplied deoxycytidine was converted to thymidine nucleotides. The present data suggest that deoxycytidine nucleotides are first deaminated to yield deoxyuridine nucleotides which can serve as substrates for both thyA- and thyB-coded synthetases. A deaminase activity for dCDP was found in crude extracts of B. subtilis. A mutant lacking the deaminase activity was unable to convert deoxycytidine nucleotides to thymidine nucleotides.