5--deoxyadenosine has been researched along with 3-methylaspartic-acid* in 2 studies
2 other study(ies) available for 5--deoxyadenosine and 3-methylaspartic-acid
| Article | Year |
|---|---|
Hydrogen tunneling in adenosylcobalamin-dependent glutamate mutase: evidence from intrinsic kinetic isotope effects measured by intramolecular competition.
Hydrogen atom transfer reactions between the substrate and coenzyme are key mechanistic features of all adenosylcobalamin-dependent enzymes. For one of these enzymes, glutamate mutase, we have investigated whether hydrogen tunneling makes a significant contribution to the mechanism by examining the temperature dependence of the deuterium kinetic isotope effect associated with the transfer of a hydrogen atom from methylaspartate to the coenzyme. To do this, we designed a novel intramolecular competition experiment that allowed us to measure the intrinsic kinetic isotope effect, even though hydrogen transfer may not be rate-determining. From the Arrhenius plot of the kinetic isotope effect, the ratio of the pre-exponential factors (A(H)/A(D)) was 0.17 +/- 0.04 and the isotope effect on the activation energy [DeltaE(a(D-H))] was 1.94 +/- 0.13 kcal/mol. The results imply that a significant degree of hydrogen tunneling occurs in glutamate mutase, even though the intrinsic kinetic isotope effects are well within the semiclassical limit and are much smaller than those measured for other AdoCbl enzymes and model reactions for which hydrogen tunneling has been implicated. Topics: Aspartic Acid; Cobamides; Deoxyadenosines; Deuterium; Hydrogen; Intramolecular Transferases; Kinetics; Models, Molecular; Temperature; Thermodynamics | 2010 |
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. Topics: Aspartic Acid; Catalysis; Clostridium; Cobamides; Deoxyadenosines; Electron Spin Resonance Spectroscopy; Glutamic Acid; Glycine; Hydrogen; Intramolecular Transferases; Methylmalonyl-CoA Mutase; Models, Chemical; Molecular Structure; Oxidation-Reduction; Propylamines; Stereoisomerism; Structure-Activity Relationship; Substrate Specificity | 2001 |