O'Donnell M E, Williams C H
Biochemistry. 1985 Dec 17;24(26):7617-21. doi: 10.1021/bi00347a018.
Thioredoxin reductase from Escherichia coli, only in its reduced state, reacts rapidly with 2 mol of N-ethylmaleimide, which specifically alkylates both active site cysteine residues. This dual modification supports previous studies indicating that a base lowers the pK of both active site cysteine residues. The dual modification also indicates that the region around the active site dithiol is more open than is the case with the related enzymes lipoamide dehydrogenase and glutathione reductase, both of which can be alkylated only on one nascent thiol. Enhanced nucleophilicity of the active site thiols is consistent with the proposed chemical mechanism of thioredoxin reductase. The sequence of the amino-terminal 16 residues is presented.
来自大肠杆菌的硫氧还蛋白还原酶，仅在其还原状态下，能与2摩尔的N - 乙基马来酰亚胺快速反应，该试剂会特异性地烷基化两个活性位点的半胱氨酸残基。这种双重修饰支持了先前的研究，表明一个碱基会降低两个活性位点半胱氨酸残基的pK值。这种双重修饰还表明，活性位点二硫醇周围的区域比相关酶硫辛酰胺脱氢酶和谷胱甘肽还原酶的情况更开放，后两者只能在一个新生硫醇上被烷基化。活性位点硫醇亲核性的增强与硫氧还蛋白还原酶提出的化学机制一致。给出了氨基末端16个残基的序列。
