engleski

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

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.

METHYLMALONYL-COA MUTASE ; DEPENDENT GLUTAMATE MUTASE ; SYNTHETIC BILAYER-MEMBRANE ; ELECTRON-PARAMAGNETIC-RESONANCE ; PARTIAL PROTON-TRANSFER ; CLOSTRIDIUM-COCHLEARIUM ; HYDROPHOBIC VITAMIN-B12 ; 2-METHYLENEGLUTARATE MUTASE ; CRYPTIC STEREOSPECIFICITY ; ESCHERICHIA-COLI

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