Determination of the structure of Escherichia coli glyoxalase I suggests a structural basis for differential metal activation
Determination of the structure of Escherichia coli glyoxalase I suggests a structural basis for differential metal activation
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DOI：
10.1021/bi000856g
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发表时间：
2000-08-01
期刊：
影响因子：
2.9
通讯作者：
Matthews, BW
中科院分区：
文献类型：
--
作者：
He, MM;Clugston, SL;Matthews, BW
金属酶glycoproteinase I（GlxI）将非酶促产生的细胞毒性甲基乙二醛和谷胱甘肽的半缩醛转化为无毒的S-D-乳酰谷胱甘肽。人GlxI，其结构已知，在Zn 2+存在下具有活性。出乎意料的是，大肠杆菌酶在Zn 2+存在下无活性，而在Ni 2+存在下活性最大。去理解金属的不同。激活，并获得了细菌酶的代表，E. coli Ni ~（2+）-GlxI。结构也已确定的载脂蛋白酶以及与Co 2+，Cd 2+，和Zn 2+的复合物。发现具有催化活性的蛋白质-金属络合物中的每一个具有八面体几何形状。这包括E.大肠杆菌酶与Ni 2+，Co 2+，和Cd 2+，以及结构报告的人Zn 2+酶。相反，E.与Zn ~（2+）配位的大肠杆菌酶具有三角双锥配位结构，无活性。这种配位模式包括四个蛋白质配体加上一个水分子。相反，在活性形式的酶的配位包括两个水分子结合到金属离子，这表明这可能是催化机制的一个关键特征。比较了人和E.大肠杆菌的酶表明，可能用于治疗用途的活性位点之间存在差异。
The metalloenzyme glyoxalase I (GlxI) converts the nonenzymatically produced hemimercaptal of cytotoxic methylglyoxal and glutathione to nontoxic S-D-lactoylglutathione. Human GlxI, for which the structure is known, is active in the presence of Zn2+. Unexpectedly, the Escherichia coli enzyme is inactive in the presence of Zn2+ and is maximally active with Ni2+. To understand this difference in metal. activation and also to obtain a representative of the bacterial enzymes, the structure of E. coli Ni2+-GlxI has been determined. Structures have also been determined for the apo enzyme as well as complexes with Co2+, Cd2+, and Zn2+. It is found that each of the protein-metal complexes that is catalytically active has octahedral geometry. This includes the complexes of the E. coli enzyme with Ni2+, Co2+, and Cd2+, as well as the structures reported for the human Zn2+ enzyme. Conversely, the complex of the E. coli enzyme with Zn2+ has trigonal bipyramidal coordination and is inactive. This mode of coordination includes four protein ligands plus a single water molecule. In contrast, the coordination in the active forms of the enzyme includes two water molecules bound to the metal ion, suggesting that this may be a key feature of the catalytic mechanism. A comparison of the human and E. coli enzymes suggests that there are differences between the active sites that might be exploited for therapeutic use.