Enzymatic Formation of 5-Fluorouracil from 1-(Tetrahydro-2-furanyl)-5-fluorouracil (Tegafur) in Human Tumor Tissues

Abstract

1-(Tetrahydro-2-furanyl)-5-fluorouracil (Tegafur) was phosphorolyzed to form 5-fluorouracil (5-FU) by a soluble fraction of human lung cancer. The catalysis was suppressed in the presence of excess thymidine, but not in the presence of 1-(2'-deoxy-β-D-glucopyranosyl) thymine, an inhibitor of uridine phosphorylases. The cleavage of Tegafur to 5-FU was assumed to be catalyzed by a thymidine phosphorylase activity, which is greatly enhanced in the human tumor tissues, and to represent a possible activation mechanism of Tegafur.