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On the Mechanism of Action of Vitamin B12: Theoretical Studies of the 2-Methyleneglutarate Mutase Catalyzed Rearrangement

Lookup NU author(s): Emeritus Professor Bernard Golding

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Abstract

Ab initio molecular orbital theory is used to investigate the coenzyme- B12-dependent rearrangement of 2-methyleneglutarate to (R)-3- methylitaconate catalyzed by 2-methyleneglutarate mutase. We use a 'model system' approach whereby substituents such as carboxylate groups are replaced by computationally less expensive hydrogen atoms. The validity of this approach is tested and supported by investigations which compare the results obtained with and without this simplification. In both rearranging systems, we find a recently suggested mechanism, involving a transient fragmentation of the substrate followed by recombination of the fragments, to be associated with a high activation energy. A cyclization/ring-opening (addition/elimination) mechanism is found to require substantially less energy than the fragmentation/recombination mechanism. Even lower in energy requirements are mechanisms involving protonation/deprotonation of the substrates.

Publication metadata

Author(s): Smith DM, Golding BT, Radom L

Publication type: Article

Publication status: Published

Journal: Journal of the American Chemical Society

Year: 1999

Volume: 121

Issue: 5

Pages: 1037-1044

Print publication date: 10/02/1999

ISSN (print): 0002-7863

ISSN (electronic): 1520-5126

Publisher: American Chemical Society

URL: .http:dx.doi.org/10.1021/ja9827245

DOI: 10.1021/ja9827245

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