Mashhadi Zahra, Newcomer Marcia E, Brash Alan R
Department of Pharmacology, Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA.
Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA.
Chembiochem. 2016 Nov 3;17(21):2000-2006. doi: 10.1002/cbic.201600345. Epub 2016 Sep 22.
This review focuses on a group of heme peroxidases that retain the catalase fold in structure, yet show little or no reaction with hydrogen peroxide. Instead of having a role in oxidative defense, these enzymes are involved in secondary metabolite biosynthesis. The prototypical enzyme is catalase-related allene oxide synthase, an enzyme that converts a specific fatty acid hydroperoxide to the corresponding allene oxide (epoxide). Other catalase-related enzymes form allylic epoxides, aldehydes, or a bicyclobutane fatty acid. In all catalases (including these relatives), a His residue on the distal face of the heme is absolutely required for activity. Its immediate neighbor in sequence as well as in 3 D space is conserved as Val in true catalases and Thr in the fatty acid hydroperoxide-metabolizing enzymes. Thr-His on the distal face of the heme is critical in switching the substrate specificity from H O to fatty acid hydroperoxide.
本综述聚焦于一类血红素过氧化物酶，它们在结构上保留了过氧化氢酶折叠，但与过氧化氢的反应很少或没有反应。这些酶并非参与氧化防御，而是参与次生代谢物的生物合成。典型的酶是过氧化氢酶相关的丙二烯氧化物合酶，该酶将特定的脂肪酸氢过氧化物转化为相应的丙二烯氧化物（环氧化物）。其他与过氧化氢酶相关的酶形成烯丙基环氧化物、醛或双环丁烷脂肪酸。在所有过氧化氢酶（包括这些相关酶）中，血红素远端表面的一个组氨酸残基对于活性是绝对必需的。在真正的过氧化氢酶中，其在序列以及三维空间中的紧邻残基保守为缬氨酸，而在脂肪酸氢过氧化物代谢酶中则为苏氨酸。血红素远端表面的苏氨酸 - 组氨酸对于将底物特异性从H₂O₂切换为脂肪酸氢过氧化物至关重要。
