Zheng Y J, Merz K M, Farber G K
152 Davey Laboratory, Department of Chemistry, Pennsylvania State University, University Park 16802.
Protein Eng. 1993 Jul;6(5):479-84. doi: 10.1093/protein/6.5.479.
Two mechanisms for an aldose-ketose isomerization have been examined using high level ab initio and semiempirical molecular orbital methods. The proton transfer pathway via an enediol intermediate is shown to be favored in the absence of a metal ion, while the hydride transfer pathway becomes favored in the presence of a metal ion. Our calculations explain why the proton transfer pathway is operative in most aldose-ketose isomerization reactions. These calculations also provide further support for the previously proposed metal ion-mediated hydride transfer mechanism for xylose isomerase.
已使用高水平从头算和半经验分子轨道方法研究了醛糖-酮糖异构化的两种机制。结果表明，在没有金属离子的情况下，经由烯二醇中间体的质子转移途径更有利，而在有金属离子的情况下，氢化物转移途径更有利。我们的计算解释了为什么质子转移途径在大多数醛糖-酮糖异构化反应中起作用。这些计算还为先前提出的木糖异构酶的金属离子介导的氢化物转移机制提供了进一步的支持。
