Hydrogen tunneling in enzyme reactions

Journal Article · Fri Mar 10 04:00:00 EST 1989 · Science (Washington, D.C.); (United States)

DOI:https://doi.org/10.1126/science.2646716· OSTI ID:6173935

Cha, Y; Murray, C J; Klinman, J P

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.

• Research Organization: Univ. of California, Berkeley (USA)
• OSTI ID: 6173935
• Journal Information: Science (Washington, D.C.); (United States), Journal Name: Science (Washington, D.C.); (United States) Vol. 243:4896; ISSN SCIEA
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALCOHOL DEHYDROGENASE
ALCOHOLS
ALDEHYDES
AROMATICS
BENZALDEHYDE
BENZYL ALCOHOL
CHEMICAL REACTIONS
ELEMENTS
ENZYME ACTIVITY
ENZYMES
EUMYCOTA
FUNGI
HEMIACETAL DEHYDROGENASES
HYDROGEN
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPE EFFECTS
LABELLED COMPOUNDS
METABOLISM
MICROORGANISMS
NONMETALS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PLANTS
REDOX REACTIONS
SACCHAROMYCES
SACCHAROMYCES CEREVISIAE
THERMODYNAMICS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
YEASTS