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

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