Gruber K, Csitkovits V, Łyskowski A, Kratky C, Kräutler B. Structure-Based Demystification of Radical Catalysis by a Coenzyme B
12 Dependent Enzyme-Crystallographic Study of Glutamate Mutase with Cofactor Homologues.
Angew Chem Int Ed Engl 2022;
61:e202208295. [PMID:
35793207 PMCID:
PMC9545868 DOI:
10.1002/anie.202208295]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Indexed: 12/04/2022]
Abstract
Catalysis by radical enzymes dependent on coenzyme B12 (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 1012 -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.
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