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Interconversion of (S)-glutamate and (2S,3S)-3-methylaspartate: a distinctive B(12)-dependent carbon-skeleton rearrangement.

Authors
  • 1
  • 1 Contribution from the Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia.
Type
Published Article
Journal
Journal of the American Chemical Society
Publication Date
Volume
123
Issue
33
Pages
7963–7972
Identifiers
PMID: 11506551
Source
Medline
License
Unknown

Abstract

The interconversion of (S)-glutamate and (2S,3S)-3-methylaspartate catalyzed by B(12)-dependent glutamate mutase is discussed using results from high-level ab initio molecular orbital calculations. Evidence is presented regarding the possible role of coenzyme-B(12) in substrate activation and product formation via radical generation. Calculated electron paramagnetic resonance parameters support experimental evidence for the involvement of substrate-derived radicals and will hopefully aid the future detection of other important radical intermediates. The height of the rearrangement barrier for a fragmentation-recombination pathway, calculated with a model that includes neutral amino and carboxylic acid substituents in the migrating glycyl group, supports recent experimental evidence for the interconversion of (S)-glutamate and (2S,3S)-3-methylaspartate through such a pathway. Our calculations suggest that the enzyme may facilitate the rearrangement of (S)-glutamate through (partial) proton-transfer processes that control the protonation state of substituents in the migrating group.

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