An inhibitory effect of thymidine on its own conversion to nucleotide in Escherichia coli.

The cellular levels of thymidine nucleotide pool in thymine-requiring mutants of Escherichia coli were followed. The pool levels of dTDP, dTTP and compound-X reached maximal values in much lower concentration of thymidine than those in thymine. In higher concentrations of thymidine, an inhibitory effect on its own conversion to nucleotide was observed. The inhibited step was suggested to be the conversion of dTMP to dTDP.