HYDROLYTIC ELIMINATION OF A MUTAGENIC NUCLEOTIDE, 8-OXODGTP, BY HUMAN 18-KILODALTON PROTEIN - SANITIZATION OF NUCLEOTIDE POOL
HYDROLYTIC ELIMINATION OF A MUTAGENIC NUCLEOTIDE, 8-OXODGTP, BY HUMAN 18-KILODALTON PROTEIN - SANITIZATION OF NUCLEOTIDE POOL
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DOI：
10.1073/pnas.89.22.11021
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发表时间：
1992-11-15
影响因子：
11.1
通讯作者：
SEKIGUCHI, M
中科院分区：
文献类型：
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作者：
MO, JY;MAKI, H;SEKIGUCHI, M
8-氧鸟嘌呤核苷酸可以与胞嘧啶和腺嘌呤核苷酸以几乎相同的效率配对。一旦8-oxodGTP在细胞核苷酸池中形成，这种突变的核苷酸就会被整合到DNA中，并会导致颠倒突变。大肠杆菌的MUT蛋白具有将8-oxodGTP水解为相应的核苷一磷酸的酶活性，因此可能是防止这种突变发生的原因。在这里，我们展示了人类细胞有一种特殊的酶，以一种类似于MUT蛋白的方式来降解8-oxodGTP。在Jurkat细胞的无细胞提取物中发现了人的8-oxodGTP酶，并将其纯化了400倍。凝胶过滤和凝胶电泳法分析表明，人8-oxodGTPase天然形式的相对分子质量为18 kDa。该酶的作用需要镁离子，最适pH为8.0。该酶能将8-oxodGTP水解为8-oxodGMP，其K(M)值为12.5um。DGTP和dATP也分别被降解为dGMP和DAMP，K(M)值是8-oxo-dGTP的70倍。DTTP和dCTP不能被水解。人类8-oxodGTP酶的这些性质与大肠杆菌MUT蛋白相似，表明保护遗传信息免受内源性氧自由基威胁的功能在生物体中广泛分布。
8-Oxoguanine nucleotide can pair with cytosine and adenine nucleotides at almost equal efficiencies. Once 8-oxodGTP is formed in the cellular nucleotide pool, this mutagenic nucleotide is incorporated into DNA and would cause transversion mutations. The MutT protein of Escherichia coli possesses enzyme activity to hydrolyze 8-oxodGTP to the corresponding nucleoside monophosphate and thus may be responsible for preventing the occurrence of such mutations. Here we show that the human cell has an enzyme specifically hydrolyzing 8-oxodGTP in a fashion similar to that seen with MutT protein. The human 8-oxodGTPase has been found in cell-free extracts from Jurkat cells and purified >400-fold. Analyses by gel filtration and gel electrophoresis revealed that the molecular mass of the native form of human 8-oxodGTPase is 18 kDa. Mg2+ ion is required for the enzyme action and the optimum pH for the reaction is pH 8.0. The enzyme hydrolyzes 8-oxodGTP to 8-oxodGMP with a K(m) value of 12.5 muM. dGTP and dATP are also degraded to dGMP and dAMP, respectively, with K(m) values 70 times greater than that for 8-oxo-dGTP. dTTP and dCTP are not hydrolyzed. These properties of the human 8-oxodGTPase are similar to those observed with the E. coli MutT protein, suggesting that the function of protecting the genetic information from the threat of endogenous oxygen radicals is widely distributed in organisms.