Danson M J, Perham R N
Biochem J. 1976 Dec 1;159(3):677-82. doi: 10.1042/bj1590677.
The reaction of two maleimides, N-ethylmaleimide and bis-(N-maleimidomethyl) ether, with the pyruvate dehydrogenase multienzyme complex of Escherichia coli in the presence of the substrate, pyruvate, was examined. In both cases, the reaction was demonstrated to be almost exclusively with the lipoate acetyltransferase component, and evidence is presented to show that the most likely sites of reaction are the lipoic acid residues covalently bound to this component. With both reagents the stoicheiometry of the reaction was measured: 2 mol of reagent reacted with each polypeptide chain of lipoate acetyltransferase, implying that each chain bears two functionally active lipolic acid residues. This observation can be reconciled with previous determinations of the lipoic acid content of the complex by allowing for the variability of the subunit polypeptide-chain ratio that can be demonstrated for this multimeric enzyme.
研究了在底物丙酮酸存在的情况下，两种马来酰亚胺（N - 乙基马来酰亚胺和双（N - 马来酰亚胺甲基）醚）与大肠杆菌丙酮酸脱氢酶多酶复合物的反应。在这两种情况下，均证明该反应几乎只与硫辛酸乙酰转移酶组分发生，并且有证据表明最可能的反应位点是与该组分共价结合的硫辛酸残基。使用这两种试剂都测定了反应的化学计量：2摩尔试剂与硫辛酸乙酰转移酶的每条多肽链反应，这意味着每条链带有两个具有功能活性的硫辛酸残基。通过考虑这种多聚酶可证明的亚基多肽链比例的变异性，这一观察结果可以与之前对该复合物硫辛酸含量的测定结果相吻合。
