Specificity of aspartokinase III from Escherichia coli and an examination of important catalytic residues.
Specificity of aspartokinase III from Escherichia coli and an examination of important catalytic residues.
复制标题
大肠杆菌天冬氨酸激酶 III 的特异性和重要催化残基的检查。
DOI：
10.1006/abbi.1996.0483
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发表时间：
1996
影响因子：
3.9
通讯作者：
Viola,RE
中科院分区：
文献类型：
--
作者：
Keng,YF;Viola,RE
天冬氨酸激酶 III (AK III) 已从含有质粒的大肠杆菌菌株中纯化出来。该酶对磷酰基受体底物显示出广泛的特异性。具有衍生化 α-羧基的天冬氨酸结构类似物被该酶接受作为替代底物。 α-氨基上的衍生物也能被 AK III 耐受，但催化活性降低。正如之前在天冬氨酸激酶 I 中观察到的那样（T. S. Angeles 和 R. E. Viola, 1992,Biochemistry31, 799），作为磷酰基受体的 β-羧基的衍生化不会阻止催化活性。这些 β-衍生化类似物能够通过区域特异性的逆转与这些酶有效结合，使 α-羧基可用作磷酰基受体。化学修饰和 pH 曲线研究已确定半胱氨酸和组氨酸的官能团参与 AK III 的催化活性。
Aspartokinase III (AK III) has been purified from a plasmid-containing strain ofEscherichia coli.The enzyme shows broad specificity for the phosphoryl acceptor substrate. Structural analogs of aspartic acid with a derivatized α-carboxyl group are accepted as alternative substrates by the enzyme. Derivatives at the α-amino group are also tolerated by AK III but with diminished catalytic activity. As has been previously observed with aspartokinase I (T. S. Angeles and R. E. Viola, 1992,Biochemistry31, 799), derivatization of the β-carboxyl group, which serves as the phosphoryl acceptor, does not prevent catalytic activity. These β-derivatized analogs are capable of productive binding to these enzymes through a reversal of regiospecificity, making the α-carboxyl group available as the phosphoryl acceptor. Chemical modification and pH profile studies have identified the functional groups of cysteine and histidine as being involved in the catalytic activity of AK III.