Department of Life Science, Graduate School of Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan.
Department of Bioscience and Biotechnology, Graduate School of Natural Science and Technology, Okayama University, Tsushima-naka, Okayama 700-8530, Japan.
Chembiochem. 2023 Jul 17;24(14):e202300021. doi: 10.1002/cbic.202300021. Epub 2023 Jun 13.
Adenosylcobalamin (AdoCbl), or coenzyme B , is a naturally occurring organometallic compound that serves as a cofactor for enzymes that catalyze intramolecular group-transfer reactions and ribonucleotide reduction in a wide variety of organisms from bacteria to animals. AdoCbl-dependent enzymes are radical enzymes that generate an adenosyl radical by homolysis of the coenzyme's cobalt-carbon (Co-C) bond for catalysis. How do the enzymes activate and cleave the Co-C bond to form the adenosyl radical? How do the enzymes utilize the high reactivity of the adenosyl radical for catalysis by suppressing undesirable side reactions? Our recent structural studies, which aimed to solve these problems with diol dehydratase and ethanolamine ammonia-lyase, established the crucial importance of the steric strain of the Co-C bond and conformational stabilization of the adenosyl radical for coenzyme B catalysis. We outline here our results obtained with these eliminating isomerases and compare them with those obtained with other radical B enzymes.
腺钴胺素（AdoCbl），或辅酶 B，是一种天然存在的有机金属化合物，作为酶的辅因子，在从细菌到动物的各种生物体中，催化分子内基团转移反应和核苷酸还原。依赖腺钴胺素的酶是自由基酶，通过辅酶的钴-碳（Co-C）键的均裂产生腺嘌呤自由基以进行催化。酶如何激活并裂解 Co-C 键以形成腺嘌呤自由基？酶如何利用腺嘌呤自由基的高反应性通过抑制不希望的副反应来进行催化？我们最近的结构研究旨在通过解决二醇脱水酶和乙醇胺氨裂解酶的这些问题，确立了 Co-C 键的空间应变和腺嘌呤自由基的构象稳定对于辅酶 B 催化的关键重要性。我们在这里概述了我们用这些消除异构酶获得的结果，并将其与用其他自由基 B 酶获得的结果进行了比较。
