Pyrimidine scavenging by Mycobacterium leprae

Summary

Mycobacterium leprae incorporated exogenously supplied pyrimidenes as bases or nucleosides, but not as a nucleotide, into its nucleic acids. Notably, thymine was incorporated ∼5 times more rapidly than thymidine by bith suspensions of, or intracellular M. leprae. Thymine incorporation was significantly inhibited by clofazamine and dapsone at near-pharmacological levels. Therefore, incorporation of thymine is preferable as an activity for assessing viability of M. leprae. Nucleosides were converted to nucleotides through kinases, bases through phosphoribosyltransferases. Alternatively, thymine and uracil could first be converted to nucleosides. Cytosine and uracil bases were interconvertable, and uracil alone could supply all the pyrimidine requirements of M. leprae, though conversion to the thymine base was extremely slow. Overall, pyrimidine scavenging occurs at a slower rate than, and appears not to be so important as purine scavenging in M. leprae.

Pyrimidine scavenging, Mycobacterium leprae