Rucker J, Cha Y, Jonsson T, Grant K L, Klinman J P
Department of Chemistry, University of California, Berkeley 94720.
Biochemistry. 1992 Nov 24;31(46):11489-99. doi: 10.1021/bi00161a030.
Previous investigations have indicated a role for hydrogen tunneling in the yeast alcohol dehydrogenase catalyzed oxidation of benzyl alcohol [Cha, Y., Murray, C. J., & Klinman, J. P. (1989) Science 243, 1325] and the bovine plasma amine oxidase catalyzed oxidation of benzylamine [Grant, K.L., & Klinman, J. P. (1989) Biochemistry 28,6597]. In the present studies, values of protium to tritium and deuterium to tritium isotope effects and their temperature dependencies have been measured using ring-substituted substrates for yeast alcohol dehydrogenase and bovine plasma amine oxidase, revealing tunneling in each case. The results of these studies indicate that hydrogen tunneling is a general phenomenon and is not limited to enzyme reactions with degenerate energy levels for bound substrates and products. An analysis of internal thermodynamics in the yeast alcohol dehydrogenase reaction shows that tunneling occurs when delta H degrees is endothermic and that the degree of tunneling appears to increase as delta H degrees decreases toward zero.
先前的研究表明，氢隧穿在酵母乙醇脱氢酶催化的苄醇氧化反应[查，Y.，默里，C. J.，& 克林曼，J. P.（1989年）《科学》243, 1325]以及牛血浆胺氧化酶催化的苄胺氧化反应[格兰特，K. L.，& 克林曼，J. P.（1989年）《生物化学》28, 6597]中发挥了作用。在本研究中，使用酵母乙醇脱氢酶和牛血浆胺氧化酶的环取代底物测量了氢与氚、氘与氚的同位素效应值及其温度依赖性，结果表明在每种情况下均存在隧穿现象。这些研究结果表明，氢隧穿是一种普遍现象，并不局限于结合底物和产物具有简并能级的酶反应。对酵母乙醇脱氢酶反应内部热力学的分析表明，当ΔH°为吸热时会发生隧穿，并且随着ΔH°向零减小，隧穿程度似乎会增加。
