Liekens S, Balzarini J, Hernández A I, De Clercq E, Priego E M, Camarasa M J, Pérez-Pérez M J
Rega Institute for Medical Research, KU Leuven, Leuven, Belgium.
Nucleosides Nucleotides Nucleic Acids. 2006;25(9-11):975-80. doi: 10.1080/15257770600888925.
We found that 5'-O-trityl-inosine (KIN59) inhibits recombinant bacterial (E. coli) and human thymidine phosphorylase (TPase) with an IC50 of 44 microM and 67 microM, respectively. In contrast to previously described TPase inhibitors, KIN59 does not compete with thymidine (dThd) at the pyrimidine nucleoside-binding site or with inorganic phosphate (Pi) at the phosphate-binding site of the enzyme. These findings are strongly suggestive for the presence of an allosteric binding site at the enzyme. TPase is identical to the angiogenic protein platelet-derived endothelial cell growth factor (PD-ECGF). As such, PD-ECGF stimulates angiogenesis in the chick chorioallantoic membrane (CAM) assay. This angiogenic response was completely inhibited by KIN59. Inosine did not inhibit the enzyme or the angiogenic effect of TPase, confirming that the 5'-O-trityl group in KIN59 is essential for the observed effect. Our observations indicate that allosteric sites in TPase may regulate its biological activity.
我们发现5'-O-三苯甲基肌苷（KIN59）对重组细菌（大肠杆菌）和人胸苷磷酸化酶（TPase）具有抑制作用，其IC50分别为44微摩尔和67微摩尔。与先前描述的TPase抑制剂不同，KIN59不在嘧啶核苷结合位点与胸苷（dThd）竞争，也不在该酶的磷酸结合位点与无机磷酸（Pi）竞争。这些发现强烈提示该酶存在变构结合位点。TPase与血管生成蛋白血小板衍生的内皮细胞生长因子（PD-ECGF）相同。因此，PD-ECGF在鸡胚绒毛尿囊膜（CAM）试验中刺激血管生成。这种血管生成反应被KIN59完全抑制。肌苷不抑制该酶或TPase的血管生成作用，证实KIN59中的5'-O-三苯甲基基团对观察到的效应至关重要。我们的观察结果表明，TPase中的变构位点可能调节其生物学活性。
