Grahame David A
Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.
Methods Enzymol. 2011;494:189-217. doi: 10.1016/B978-0-12-385112-3.00010-X.
The nickel- and iron-containing enzyme acetyl-CoA synthase (ACS) catalyzes de novo synthesis as well as overall cleavage of acetyl-CoA in acetogens, various other anaerobic bacteria, methanogens, and other archaea. The enzyme contains a unique active site metal cluster, designated the A cluster, that consists of a binuclear Ni-Ni center bridged to an [Fe(4)S(4)] cluster. In bacteria, ACS is tightly associated with CO dehydrogenase to form the bifunctional heterotetrameric enzyme CODH/ACS, whereas in archaea, ACS is a component of the large multienzyme complex acetyl-CoA decarbonylase/synthase (ACDS), which comprises five different subunits that make up the subcomponent proteins ACS, CODH, and a corrinoid enzyme. Characteristic properties of ACS are discussed, and key methods are described for analysis of the enzyme's multiple redox-dependent activities, including overall acetyl-CoA synthesis, acetyltransferase, and an isotopic exchange reaction between the carbonyl group of acetyl-CoA and CO. Systematic measurement of these activities, applied to different ACS protein forms, provides insight into the ACS catalytic mechanism and physiological functions in both CODH/ACS and ACDS systems.
含镍和铁的酶乙酰辅酶A合成酶（ACS）催化产乙酸菌、其他各种厌氧菌、产甲烷菌及其他古菌中乙酰辅酶A的从头合成以及整体裂解。该酶含有一个独特的活性位点金属簇，称为A簇，它由一个双核Ni-Ni中心与一个[Fe(4)S(4)]簇桥连而成。在细菌中，ACS与一氧化碳脱氢酶紧密结合形成双功能异源四聚体酶CODH/ACS，而在古菌中，ACS是大型多酶复合体乙酰辅酶A脱羰酶/合成酶（ACDS）的一个组分，该复合体由五个不同的亚基组成，这些亚基构成了亚组分蛋白ACS、CODH和一种类咕啉酶。文中讨论了ACS的特性，并描述了用于分析该酶多种氧化还原依赖性活性的关键方法，包括整体乙酰辅酶A合成、乙酰转移酶活性以及乙酰辅酶A羰基与CO之间的同位素交换反应。将这些活性的系统测量应用于不同的ACS蛋白形式，有助于深入了解CODH/ACS和ACDS系统中ACS的催化机制和生理功能。
