Substrate specificity of thymidine phosphorylase of E. coli: role of hydroxyl groups.

Substrate specificity of E. coli thymidine phosphorylase to pyrimidine nucleoside modified at 5'-, 3'-, and 2'-positions of sugar moiety has been studied. Equilibrium (K(eq)) and kinetics constants of phosphorolysis reaction of nucleosides were measured. The most important hydrogen bonds in enzyme-substrate complex have been determined.