7-Deazaxanthine, a novel prototype inhibitor of thymidine phosphorylase

7-Deazaxanthine (7DX) was identified as a novel inhibitor of thymidine (dThd) phosphorylase (TPase). It inhibited the TPase reaction in a concentration-dependent manner. At 1 mM, it almost completely prevented the TPase-catalysed hydrolysis of dThd to thymine. The 50% inhibitory concentration (IC50) Of 7DX was 40 mu M in the presence of 100 mu M of the natural substrate dThd. 7DX is also endowed with a marked inhibitory effect on angiogenesis. It significantly prevents neovascularisation in the chicken chorioallantoic membrane during development. 7DX is the first purine derivative shown to be a potent inhibitor of purified TPase and angiogenesis. (C) 1998 Federation of European Biochemical Societies.