Large kinetic isotope effects in enzymatic proton transfer and the role of substrate oscillations

Dimitri Antoniou, Steven D. Schwartz

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122 Scopus citations


We propose an interpretation of the experimental findings of Klinman and coworkers [Cha, Y., Murray, C. J. and Klinman, J.P. (1989) Science 243, 1325- 1330; Grant, K. L. and Klinman, J.P. (1989) Biochemistry 28, 6597-6605; and Bahnson, B. J. and Klinman, J.P. (1995) Methods Enzymol. 249, 373.-397], who showed that proton transfer reactions that are catalyzed by bovine serum amine oxidase proceed through tunneling. We show that two different tunneling models are consistent with the experiments. In the first model, the proton tunnels from the ground state. The temperature dependence of the kinetic isotope effect is caused by a thermally excited substrate mode that modulates the barrier, as has been suggested by Borgis and Hynes [Borgis, D. and Hynes, J. T. (1991) J. Chem. Phys. 94, 3619-3628]. In the second model, there is both over-the-barrier transfer and tunneling from excited states. Finally, we propose two experiments that can distinguish between the possible mechanisms.

Original languageEnglish (US)
Pages (from-to)12360-12365
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number23
StatePublished - Nov 11 1997

ASJC Scopus subject areas

  • General


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