ABSTRACT
I. Introduction ...................................................................................................................... 725
II. Observations ..................................................................................................................... 727
A. Rate Constants.......................................................................................................... 727
B. Kinetic Isotope Effects............................................................................................. 728
C. Temperature Dependence ........................................................................................ 728
D. Systems without Proteins......................................................................................... 729
III. Theoretical Models .......................................................................................................... 730
A. Two-Oscillator Models ............................................................................................ 730
B. Golden Rule Treatment............................................................................................ 731
C. Semiclassical Instanton Approach ........................................................................... 734
D. Model Parameters .................................................................................................... 734
IV. Applications...................................................................................................................... 735
A. Coenzyme B
.......................................................................................................... 735
B. Lipoxygenase ........................................................................................................... 736
C. Primary Amine Dehydrogenases ............................................................................. 737
D. Dicopper Complexes................................................................................................ 738
V. Discussion ........................................................................................................................ 738
Acknowledgments ........................................................................................................................ 739
References..................................................................................................................................... 739
Deuterium-labeling of substrates is an effective way to gather information on enzymatic reactions
involving hydrogen transfer. If deuterium substitution reduces the rate of the reaction substantially,
it implies that hydrogen transfer is a rate-determining step and that this step proceeds by quantum-
mechanical tunneling. Large kinetic effects of deuterium substitution are observed in reactions in
which a carbon-hydrogen bond is broken.
