Department of Picobiology/Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo, 678-1297, Japan.
The RIKEN SPring-8 Center, 1-1-1 Koto, Sayo-cho, Sato-gun, Hyogo, 678-5248, Japan.
Angew Chem Int Ed Engl. 2018 Jun 25;57(26):7830-7835. doi: 10.1002/anie.201803591. Epub 2018 May 25.
The crystal structures of the B -dependent isomerases (eliminating) diol dehydratase and ethanolamine ammonia-lyase complexed with adenosylcobalamin were solved with and without substrates. The structures revealed that the peripheral a-acetamide side chain of the corrin ring directly interacts with the adenosyl group to maintain the group in the catalytic position, and that this side chain swings between the original and catalytic positions in a synchronized manner with the radical shuttling between the coenzyme and substrate/product. Mutations involving key residues that cooperatively participate in the positioning of the adenosyl group, directly or indirectly through the interaction with the a-side chain, decreased the turnover rate and increased the relative rate of irreversible inactivation caused by undesirable side reactions. These findings guide the engineering of enzymes for improved catalysis and producing useful chemicals by utilizing the high reactivity of radical species.
结合和不结合底物，解决了 B 依赖性异构酶（消除）二醇脱水酶和乙醇胺氨裂解酶与腺苷钴胺素复合物的晶体结构。这些结构表明，钴胺环的外围 a-乙酰胺侧链直接与腺苷基相互作用，以将其保持在催化位置，并且该侧链与自由基在辅酶和底物/产物之间穿梭同步地在原始和催化位置之间摆动。涉及共同参与腺苷基定位的关键残基的突变，直接或间接通过与 a-侧链的相互作用，降低了周转率，并增加了由不需要的副反应引起的不可逆失活的相对速率。这些发现指导了通过利用自由基的高反应性来设计酶以提高催化作用和生产有用化学品的工程。
