The oxidized forms of dATP are substrates for the human MutT homologue, the hMTH1 protein
The oxidized forms of dATP are substrates for the human MutT homologue, the hMTH1 protein
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DOI：
10.1074/jbc.274.26.18201
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发表时间：
1999-06-25
影响因子：
4.8
通讯作者：
Kasai, H
中科院分区：
文献类型：
--
作者：
Fujikawa, K;Kamiya, H;Kasai, H
研究了大肠杆菌 MutT 和人 MTH1 (hMTH1) 水解除 8-羟基-dGTP (8-OH-dGTP) 之外的氧化 DNA 前体的可能性。我们在此报告hMTH1水解2-羟基-dATP (2-OH-dATP)和8-羟基-dATP (8-OH-dATP)，即dATP的氧化形式，但不水解(R)-8,5'-cyclod-dATP、5-羟基-dCTP和8-甲酰基-dUTP。动力学参数表明，2-OH-dATP 比 8-OH-dGTP 水解效率更高，亲和力更高。 8-OH-dATP 的水解效率与 8-OH-dGTP 相同。在所有测试的 pH 值（pH 7.2 至 pH 8.8）下均观察到 2-OH-dATP 比 8-OH-dGTP 优先水解。特别是，在 pH 7.2 时，2-OH-dATP 的水解效率比 8-OH-dGTP 的水解效率有 5 倍的差异。然而，大肠杆菌 MutT 对 2-OH-dATP 或 8-OH-dATP 没有水解活性。因此，大肠杆菌 MutT 是 hMTH1 的不完美对应物。此外，我们发现2-羟基-dADP和8-羟基-dGDP竞争性抑制hMTH1的8-OH-dATP水解酶和8-OH-dGTP水解酶活性。 2-羟基-dADP 的抑制作用比 8-羟基-dGDP 强 S 倍。这些结果表明，三个受损的核苷酸共享 hMTH1 的相同识别位点，并且它是一种比迄今为止预期更重要的消毒酶。
The possibility that Escherichia coli MutT and human MTH1 (hMTH1) hydrolyze oxidized DNA precursors other than 8-hydroxy-dGTP (8-OH-dGTP) was investigated. We report here that hMTH1 hydrolyzed 2-hydroxy-dATP (2-OH-dATP) and 8-hydroxy-dATP (8-OH-dATP), oxidized forms of dATP, but not (R)-8,5'-cyclod-dATP, 5-hydroxy-dCTP, and 8-formyl-dUTP. The kinetic parameters indicated that 2-OH-dATP was hydrolyzed more efficiently and with higher affinity than 8-OH-dGTP. 8-OH-dATP was hydrolyzed as efficiently as 8-OH-dGTP. The preferential hydrolysis of 2-OH-dATP over 8-OH-dGTP was observed at all of the pH values tested (pH 7.2 to pH 8.8). In particular, a 5-fold difference in the hydrolysis efficiencies for 2-OH-dATP over 8-OH-dGTP was found at pH 7.2. However, E. coli MutT had no hydrolysis activity for either 2-OH-dATP or 8-OH-dATP. Thus, E. coli MutT is an imperfect counterpart for hMTH1. Furthermore, we found that 2-hydroxy-dADP and 8-hydroxy-dGDP competitively inhibited both the 8-OH-dATP hydrolase and 8-OH-dGTP hydrolase activities of hMTH1. The inhibitory effects of 2-hydroxy-dADP were S-fold stronger than those of 8-hydroxy-dGDP, These results suggest that the three damaged nucleotides share the same recognition site of hMTH1 and that it is a more important sanitization enzyme than expected thus far.