13C isotope effect on the reaction catalyzed by prephenate dehydratase
| Autor: | Peter Kast, W. W. Cleland, Andreas C. Kleeb, Jeremy Van Vleet, Donald Hilvert |
|---|---|
| Rok vydání: | 2010 |
| Předmět: |
Threonine
Stereochemistry Archaeal Proteins Entropy Biophysics Entropy of activation Prephenate dehydratase Biochemistry Article Catalysis Analytical Chemistry 03 medical and health sciences Catalytic Domain Kinetic isotope effect Side chain Molecular Biology 030304 developmental biology 0303 health sciences Carbon Isotopes biology Chemistry 030302 biochemistry & molecular biology Methanococcales Methanocaldococcus jannaschii biology.organism_classification Prephenate Dehydratase Recombinant Proteins Enzyme Activation Kinetics Entropy (order and disorder) |
| Zdroj: | Biochimica et Biophysica Acta |
| DOI: | 10.1016/j.bbapap.2009.11.018 |
| Popis: | The (13)C isotope effect for the conversion of prephenate to phenylpyruvate by the enzyme prephenate dehydratase from Methanocaldococcus jannaschii is 1.0334+/-0.0006. The size of this isotope effect suggests that the reaction is concerted. From the X-ray structure of a related enzyme, it appears that the only residue capable of acting as the general acid needed for removal of the hydroxyl group is threonine-172, which is contained in a conserved TRF motif. The more favorable entropy of activation for the enzyme-catalyzed process (25 eu larger than for the acid-catalyzed reaction) has been explained by a preorganized microenvironment that obviates the need for extensive solvent reorganization. This is consistent with forced planarity of the ring and side chain, which would place the leaving carboxyl and hydroxyl out of plane. Such distortion of the substrate may be a major contributor to catalysis. |
| Databáze: | OpenAIRE |
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