Gruber Karl, Csitkovits Vanessa, Łyskowski Andrzej, Kratky Christoph, Kräutler Bernhard
Institute of Molecular Biosciences University of Graz Humboldtstraße 50 8010 Graz Austria.
BioTechMed-Graz 8010 Graz Austria.
Angew Chem Weinheim Bergstr Ger. 2022 Aug 26;134(35):e202208295. doi: 10.1002/ange.202208295. Epub 2022 Jul 21.
Catalysis by radical enzymes dependent on coenzyme B (AdoCbl) relies on the reactive primary 5'-deoxy-5'adenosyl radical, which originates from reversible Co-C bond homolysis of AdoCbl. This bond homolysis is accelerated roughly 10-fold upon binding the enzyme substrate. The structural basis for this activation is still strikingly enigmatic. As revealed here, a displaced firm adenosine binding cavity in substrate-loaded glutamate mutase (GM) causes a structural misfit for intact AdoCbl that is relieved by the homolytic Co-C bond cleavage. Strategically interacting adjacent adenosine- and substrate-binding protein cavities provide a tight caged radical reaction space, controlling the entire radical path. The GM active site is perfectly structured for promoting radical catalysis, including "negative catalysis", a paradigm for AdoCbl-dependent mutases.
依赖辅酶B（腺苷钴胺素，AdoCbl）的自由基酶催化作用依赖于具有反应活性的伯5'-脱氧-5'-腺苷自由基，该自由基源自AdoCbl中Co-C键的可逆均裂。在结合酶底物后，这种键的均裂速度大约加快10倍。这种激活作用的结构基础仍然非常神秘。正如本文所揭示的，在底物负载的谷氨酸变位酶（GM）中，腺苷结合腔移位导致完整的AdoCbl出现结构错配，而这种错配通过Co-C键的均裂得以缓解。策略性相互作用的相邻腺苷和底物结合蛋白腔提供了一个紧密的笼状自由基反应空间，控制着整个自由基路径。GM活性位点的结构完美，有利于促进自由基催化，包括“负催化”，这是AdoCbl依赖性变位酶的一种模式。
