Szilák L, Venetianer P, Kiss A
Institute of Biochemistry, Hungarian Academy of Sciences, Szeged.
Eur J Biochem. 1992 Oct 1;209(1):391-7. doi: 10.1111/j.1432-1033.1992.tb17301.x.
The EcaI GGTNACC-specific DNA-adenine modification methyltransferase has been purified to apparent homogeneity. The active form of the DNA methyltransferase is a single polypeptide. The enzyme has a pH optimum at pH 8.0 and a temperature optimum at 25 degrees C. EcaI DNA methyltransferase transfers one methyl group to the adenine of the recognition site in a single binding event. The Km was 170 nM for DNA and 1.8 microM for the methyl donor S-adenosylmethionine. Methylated DNA is a competitive inhibitor with respect to DNA (Ki = 3.5 nM). The other product of the DNA-methylation reaction, S-adenosylhomocysteine was found to be a competitive inhibitor with respect to S-adenosylmethionine (Ki = 2.7 microM). The S-adenosylmethionine analog sinefungin was shown to be a very strong inhibitor (Ki = 3.5 nM) of the DNA methyltransferase reaction.
EcaI特异性识别GGTNACC的DNA腺嘌呤修饰甲基转移酶已被纯化至表观均一。DNA甲基转移酶的活性形式为单一多肽。该酶的最适pH为8.0，最适温度为25℃。EcaI DNA甲基转移酶在单次结合事件中将一个甲基转移至识别位点的腺嘌呤上。对DNA的Km为170 nM，对甲基供体S-腺苷甲硫氨酸的Km为1.8 μM。甲基化DNA对DNA而言是竞争性抑制剂（Ki = 3.5 nM）。发现DNA甲基化反应的另一产物S-腺苷高半胱氨酸对S-腺苷甲硫氨酸而言是竞争性抑制剂（Ki = 2.7 μM）。S-腺苷甲硫氨酸类似物杀稻瘟菌素被证明是DNA甲基转移酶反应的一种非常强效的抑制剂（Ki = 3.5 nM）。
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