Koschorreck Katja, Alpdagtas Saadet, Urlacher Vlada B
Institute of Biochemistry, Heinrich-Heine-University Düsseldorf, Universitätsstraße 1, Düsseldorf 40225, Germany.
Department of Biology, Van Yuzuncu Yil University, Van 65080, Turkey.
Eng Microbiol. 2022 Jul 28;2(3):100037. doi: 10.1016/j.engmic.2022.100037. eCollection 2022 Sep.
Copper-radical oxidases (CROs) catalyze the two-electron oxidation of a large number of primary alcohols including carbohydrates, polyols and benzylic alcohols as well as aldehydes and α-hydroxy-carbonyl compounds while reducing molecular oxygen to hydrogen peroxide. Initially, CROs like galactose oxidase and glyoxal oxidase were identified only in fungal secretomes. Since the last decade, their representatives have also been identified in some bacteria. CROs are grouped in the AA5 family of "auxiliary activities" in the database of Carbohydrate-Active enzymes. Despite low overall sequence similarity and different substrate specificities, sequence alignments and the solved crystal structures revealed a conserved architecture of the active sites in all CROs, with a mononuclear copper ion coordinated to an axial tyrosine, two histidines, and a cross-linked cysteine-tyrosyl radical cofactor. This unique post-translationally modified protein cofactor has attracted much attention in the past, which resulted in a large number of reports that shed light on key steps of the catalytic cycle and physico-chemical properties of CROs. Thanks to their broad substrate spectrum accompanied by the only need for molecular oxygen for catalysis, CROs since recently experience a renaissance and have been applied in various biocatalytic processes. This review provides an overview of the structural features, catalytic mechanism and substrates of CROs, presents an update on the engineering of these enzymes to improve their expression in recombinant hosts and to enhance their activity, and describes their potential fields of biotechnological application.
铜自由基氧化酶（CROs）催化包括碳水化合物、多元醇和苄醇以及醛和α-羟基羰基化合物在内的大量伯醇的双电子氧化，同时将分子氧还原为过氧化氢。最初，像半乳糖氧化酶和乙二醛氧化酶这样的CROs仅在真菌分泌组中被鉴定出来。自过去十年以来，它们的代表也在一些细菌中被鉴定出来。在碳水化合物活性酶数据库中，CROs被归类于“辅助活性”的AA5家族。尽管总体序列相似性较低且底物特异性不同，但序列比对和已解析的晶体结构揭示了所有CROs活性位点的保守结构，其中单核铜离子与一个轴向酪氨酸、两个组氨酸以及一个交联的半胱氨酸 - 酪氨酸自由基辅因子配位。这种独特的翻译后修饰蛋白质辅因子在过去引起了广泛关注，这导致了大量揭示CROs催化循环关键步骤和物理化学性质的报道。由于其广泛的底物谱以及催化仅需分子氧，CROs最近经历了复兴，并已应用于各种生物催化过程。本综述概述了CROs的结构特征、催化机制和底物，介绍了这些酶工程改造的最新进展，以提高它们在重组宿主中的表达并增强其活性，并描述了它们在生物技术应用中的潜在领域。
