Lanz Nicholas D, Booker Squire J
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.
Biochim Biophys Acta. 2012 Nov;1824(11):1196-212. doi: 10.1016/j.bbapap.2012.07.009. Epub 2012 Jul 28.
Radical SAM (RS) enzymes use a 5'-deoxyadenosyl 5'-radical generated from a reductive cleavage of S-adenosyl-l-methionine to catalyze over 40 distinct reaction types. A distinguishing feature of these enzymes is a [4Fe-4S] cluster to which each of three iron ions is ligated by three cysteinyl residues most often located in a Cx(3)Cx(2)C motif. The α-amino and α-carboxylate groups of SAM anchor the molecule to the remaining iron ion, which presumably facilitates its reductive cleavage. A subset of RS enzymes contains additional iron-sulfur clusters, - which we term auxiliary clusters - most of which have unidentified functions. Enzymes in this subset are involved in cofactor biosynthesis and maturation, post-transcriptional and post-translational modification, enzyme activation, and antibiotic biosynthesis. The additional clusters in these enzymes have been proposed to function in sulfur donation, electron transfer, and substrate anchoring. This review will highlight evidence supporting the presence of multiple iron-sulfur clusters in these enzymes as well as their predicted roles in catalysis. This article is part of a special issue entitled: Radical SAM enzymes and radical enzymology.
自由基S-腺苷甲硫氨酸（RS）酶利用由S-腺苷-L-甲硫氨酸的还原性裂解产生的5'-脱氧腺苷5'-自由基来催化40多种不同类型的反应。这些酶的一个显著特征是一个[4Fe-4S]簇，其中三个铁离子中的每一个都由三个最常位于Cx(3)Cx(2)C基序中的半胱氨酰残基连接。SAM的α-氨基和α-羧基将分子锚定到剩余的铁离子上，这可能有助于其还原性裂解。RS酶的一个子集包含额外的铁硫簇，我们将其称为辅助簇，其中大多数功能不明。该子集中的酶参与辅因子生物合成和成熟、转录后和翻译后修饰、酶激活以及抗生素生物合成。这些酶中的额外簇被认为在硫供体、电子转移和底物锚定中发挥作用。本综述将重点介绍支持这些酶中存在多个铁硫簇的证据及其在催化中的预测作用。本文是名为：自由基SAM酶与自由基酶学的特刊的一部分。
