Thymidine phosphorylase. Substrate specificity for 5-substituted 2'-deoxyuridines

A continuous spectrophotometric assay for thymidine phosphorylase has been developed and used to analyze the substrate properties of a number of 5-substituted 2'-deoxyuridines. A QSAR was found which relates the catalytic efficiency for various substrates to a single variable, the inductive field constant F.