[Arg292----Val] or [Arg292----Leu] mutation enhances the reactivity of Escherichia coli aspartate aminotransferase with aromatic amino acids.
[Arg292----Val] or [Arg292----Leu] mutation enhances the reactivity of Escherichia coli aspartate aminotransferase with aromatic amino acids.
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[Arg292----Val]或[Arg292----Leu]突变增强了大肠杆菌天冬氨酸转氨酶与芳香族氨基酸的反应性。
DOI：
10.1016/0006-291x(89)92443-1
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发表时间：
1989
影响因子：
3.1
通讯作者：
H. Kagamiyama
中科院分区：
文献类型：
--
作者：
H. Hayashi;S. Kuramitsu;Y. Inoue;Y. Morino;H. Kagamiyama
通过定点诱变将大肠杆菌天冬氨酸转氨酶的 Arg292 替换为缬氨酸或亮氨酸。与野生型酶相比，两种突变酶的天冬氨酸和谷氨酸的 k cat K m 值均显示出超过 5 个数量级的降低。这支持了这样的论点：Arg292 对于确定该酶对二羧酸底物的特异性非常重要。相比之下，以芳香族氨基酸为底物时，突变酶的 k cat K m 值增加了 5 至 10 倍。因此，将不带电的疏水侧链引入292位会导致该酶的底物特异性发生显着改变，从而提高对芳香族氨基酸的催化效率。
Arg292 of E., coli aspartate aminotransferase was substituted with valine or leucine by site-directed mutagenesis. In comparison with the wild-type enzyme, either of the mutant enzymes showed a decrease by over 5 orders of magnitude of k cat K m values for aspartate and glutamate. This supports the contention that Arg292 is important for determining the specificity of this enzyme for dicarboxylic substrates. In contrast, mutant enzymes displayed a 5-to 10-fold increase in k cat K m values for aromatic amino acids as substrates. Thus, introduction of an uncharged, hydrophobic side chain into position 292 leads to a striking alteration in substrate specificity of this enzyme, thereby improving catalytic efficiency toward aromatic amino acids.