Brooks R R
Biochem J. 1979 Oct 1;183(1):65-71. doi: 10.1042/bj1830065.
Sixteen compounds related to GTP were evaluated as inhibitors of bacteriophage-Q beta poly(C)-dependent poly(G) polymerase. Non-phosphorylated compounds, including guanine, guanosine and deoxyguanosine, were inactive. Phosphorylated compounds gave significant inhibition at millimolar concentrations. For nucleotides the feature important for inhibition was the 5'-phosphate chain. Four triphosphates, XTP, ITP, 7-methyl-GTP and 2'-O-methyl-GTP, gave 50% inhibition of both the poly(C)- and poly(U2,C)-dependent reactions at concentrations from 0.1 to 5 mM. XTP was 10-fold more potent an inhibitor of the reaction with poly(U2,C) as template. None of these four compounds was able to substitute for GTP as substrate to a significant extent. The most active compound, 2'-O-methyl-GTP, was a competitive inhibitor (Ki = 0.4 mM) of GTP in the poly(C)-dependent reaction.
对16种与GTP相关的化合物进行了评估，以确定它们作为噬菌体-Qβ聚（C）依赖性聚（G）聚合酶抑制剂的活性。包括鸟嘌呤、鸟苷和脱氧鸟苷在内的非磷酸化化合物没有活性。磷酸化化合物在毫摩尔浓度下有显著抑制作用。对于核苷酸来说，抑制作用的重要特征是5'-磷酸链。四种三磷酸核苷酸，即XTP、ITP、7-甲基-GTP和2'-O-甲基-GTP，在0.1至5 mM的浓度下对聚（C）依赖性反应和聚（U2,C）依赖性反应均有50%的抑制作用。XTP作为以聚（U2,C）为模板的反应抑制剂，其效力比其他三种化合物高10倍。这四种化合物均不能在很大程度上替代GTP作为底物。活性最高的化合物2'-O-甲基-GTP是聚（C）依赖性反应中GTP的竞争性抑制剂（Ki = 0.4 mM）。
