Contrasting Values of Commitment Factors Measured from Viscosity, pH, and Kinetic Isotope Effects: Evidence for Slow Conformational Changes in theD-Amino Acid Oxidase Reaction
✍ Scribed by Paul F. Fitzpatrick; Kevin A. Kurtz; John M. Denu; John F. Emanuele Jr.
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 187 KB
- Volume
- 25
- Category
- Article
- ISSN
- 0045-2068
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✦ Synopsis
The flavoprotein D-amino acid oxidase catalyzes the oxidation of D-amino acids to imino acids. Previous studies of pH and isotope effets on the reaction with D-alanine as substrate have established that the enzyme substrate complex partitions forward toward carbon-hydrogen bond cleavage 10 times as fast as the amino acid dissociates and that overall turnover is limited by product release. However, the V/K value for D-alanine is not affected by the solution viscosity, while the V max value is only 15% limited by diffusion. These results are interpreted as evidence for a protein conformational change between an open conformation which binds substrates and a closed complex within which catalysis occurs. Such a model is supported by the recently reported structure of the enzyme-benzoate complex (A. Mattevi,