Hydrogen tunneling in enzyme reactions.
Primary and secondary protium-to-tritium (H/T) and deuterium-to-tritium (D/T) kinetic isotope effects for the catalytic oxidation of benzyl alcohol to benzaldehyde by yeast alcohol dehydrogenase (YADH) at 25 degrees Celsius have been determined. Previous studies showed that this reaction is nearly or fully rate limited by the hydrogen-transfer step. Semiclassical mass considerations that do not include tunneling effects would predict that kH/kT = (kD/kT)3.26, where kH, kD, and kT are the rate constants for the reaction of protium, deuterium, and tritium derivatives, respectively. Significant deviations from this relation have now been observed for both primary and especially secondary effects, such that experimental H/T ratios are much greater than those calculated from the above expression. These deviations also hold in the temperature range from 0 to 40 degrees Celsius. Such deviations were previously predicted to result from a reaction coordinate containing a significant contribution from hydrogen tunneling.[1]References
- Hydrogen tunneling in enzyme reactions. Cha, Y., Murray, C.J., Klinman, J.P. Science (1989) [Pubmed]
Annotations and hyperlinks in this abstract are from individual authors of WikiGenes or automatically generated by the WikiGenes Data Mining Engine. The abstract is from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.About WikiGenesOpen Access LicencePrivacy PolicyTerms of Useapsburg
