The crotonases comprise a widely distributed enzyme superfamily that has multiple roles in both primary and secondary metabolism. Many crotonases employ oxyanion hole-mediated stabilization of intermediates to catalyze the reaction of coenzyme A (CoA) thioester substrates (e.g., malonyl-CoA, α,β-unsaturated CoA esters) both with nucleophiles and, in the case of enolate intermediates, with varied electrophiles. Reactions of crotonases that proceed via a stabilized oxyanion intermediate include the hydrolysis of substrates including proteins, as well as hydration, isomerization, nucleophilic aromatic substitution, Claisen-type, and cofactor-independent oxidation reactions. The crotonases have a conserved fold formed from a central β-sheet core surrounded by α-helices, which typically oligomerizes to form a trimer or dimer of trimers. The presence of a common structural platform and mechanisms involving intermediates with diverse reactivity implies that crotonases have considerable potential for biocatalysis and synthetic biology, as supported by pioneering protein engineering studies on them. In this Perspective, we give an overview of crotonase diversity and structural biology and then illustrate the scope of crotonase catalysis and potential for biocatalysis.

中文翻译：

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crotonases：大自然的可转换催化剂

所述巴豆酶包含广泛分布的酶超家族，其在初级和次级代谢中均具有多种作用。许多巴豆酶采用氧阴离子孔介导的中间体稳定作用来催化辅酶A（CoA）硫酯底物（例如丙二酰辅酶A，α，β-不饱和CoA酯）与亲核试剂的反应，以及在烯醇化中间体的情况下各种亲电试剂。经由稳定的氧阴离子中间体进行的巴豆酶的反应包括包括蛋白质在内的底物的水解，以及水合，异构化，亲核芳族取代，克莱森型和不依赖辅因子的氧化反应。所述巴豆酶具有由被α-螺旋包围的中央β-折叠核心形成的保守折叠，所述α-螺旋通常寡聚形成三聚体或三聚体。共同的结构平台和机制的存在涉及具有不同反应性的中间体，这表明巴豆酶具有开创性的蛋白质工程学研究的支持，对生物催化和合成生物学具有相当大的潜力。在此观点中，我们概述了巴豆酶的多样性和结构生物学，然后说明了巴豆酶催化的范围和生物催化的潜力。