Site-specific mutagenesis of two histidine residues in fatty acid ethyl ester synthase-III.
Site-specific mutagenesis of two histidine residues in fatty acid ethyl ester synthase-III.
复制标题
脂肪酸乙酯合酶-III 中两个组氨酸残基的定点诱变。
DOI：
10.1016/0006-291x(92)90647-4
复制
发表时间：
1992
影响因子：
3.1
通讯作者：
Lange,LG
中科院分区：
文献类型：
--
作者：
Bora,PS;Wu,X;Lange,LG
人心肌脂肪酸乙酯合成酶-III是新近发现的一种酸性谷胱甘肽S转移酶，可同时代谢乙醇和致癌物。目前还没有对这两种不同的酶活性进行结构-功能研究。由于在脂肪酸乙酯合成酶-III(His 72和His 163)中只有两个组氨酸残基，因此通过定点突变来研究每一个残基的作用。在标准测定条件下，72位突变的脂肪酸乙酯合成酶-III含有谷氨酰胺、丙氨酸或丙氨酸，其谷胱甘肽S转移酶活性低于对照的5%，但仍保持脂肪酸乙酯合成酶活性。相反，用Pro取代组氨酸163对谷胱甘肽S转移酶活性没有影响，但略有增加合成酶活性。因此，本研究表明组氨酸在脂肪酸乙酯合成酶III中的作用取决于亲核底物的不同。
Human myocardial fatty acid ethyl ester synthase-III is a newly described acidic glutathione S-transferase that metabolizes both ethanol and carcinogens. Structure-function studies have not been performed relating these two distinct enzymatic activities. Since there are only two histidine residues in fatty acid ethyl ester synthase-III (His 72 and His 163), the role of each was examined by site-specific mutagenesis. Fatty acid ethyl ester synthase-III mutagenized at position 72 to contain either Gln, Pro or Ala had less than 5% of control glutathione S-transferase activity but retained fatty acid ethyl ester synthase activity under standard assay conditions. In contrast, substitution of histidine 163 with proline had no effect on glutathione S-transferase activity, but it slightly increased synthase activity. Thus, this study indicates that histidine plays a differential role in fatty acid ethyl ester synthase III depending on the nucleophilic substrate.