Thymidine phosphorylase (TPase, EC 2.4.2.4) catalyses the reversible phosphorolysis of (substituted)uracil 2'-deoxynucleosides forming 2-deoxyribose-1-phosphate and (substituted)uracil, thus providing both catabolic and salvage routes for pyrimidines. We now report detailed inhibition kinetics of TPI towards TPase from E. coli in detail, as well as those for analogs1.



5-Chloro-6-(2-imino-pyrrolidin-1-yl)methyl-uracil hydrochloride [TPI,1] and its 5-bromo analogue [2], as well as 6-(2-amino-imidazol-1-yl)methyl-5-bromo-uracil [3] and its 2-chloro analogue [4], plus their exocyclic guanidino analogues [5,6], were found to act as strong inhibitors. Detailed studies showed the inhibition was effectively irreversible under the assay conditions used and was stoichiometric. Thus they provide the first active-site titrants of recombinant E. coli thymidine phosphorylase.

References and Footnotes

1. P. Reigan, P. N. Edwards, A. Gbaj, C. Cole, S. T. Barry, K. M. Page, S. E. Ashton, R. W. A. Luke, K. T. Douglas, I. J. Stratford, M. Jaffar, R. A. Bryce, and S. Freeman. J. Med. Chem. 48, 392-402 (2005).