Xie Yuchun, Das Prasanta Kumar, Caaveiro Jose M M, Klibanov Alexander M
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Biotechnol Bioeng. 2002 Jul 5;79(1):105-11. doi: 10.1002/bit.10308.
Lyophilized horseradish peroxidase (HRP) exhibits poor stereoselectivity in the sulfoxidation of thioanisole when the enzyme is either redissolved in water or suspended in organic solvents. However, when HRP is co-lyophilized in the presence of lyoprotectants or ligands, its stereoselectivity, although still low in most organic solvents, increases up to 4-fold if assayed in secondary or tertiary alcohols (but not in their linear isomers). A mechanistic hypothesis is presented explaining this puzzling phenomenon on the basis of a model of the active site of the enzyme-substrate complex derived from its X-ray crystal structure by means of molecular dynamics and energy minimization.
当冻干的辣根过氧化物酶（HRP）重新溶解于水或悬浮于有机溶剂中时，它在硫代苯甲醚的亚砜化反应中表现出较差的立体选择性。然而，当HRP在冻干保护剂或配体存在的情况下进行共冻干时，其立体选择性虽然在大多数有机溶剂中仍然较低，但如果在仲醇或叔醇（而非其直链异构体）中进行测定，其立体选择性会提高至4倍。本文基于通过分子动力学和能量最小化从酶-底物复合物的X射线晶体结构推导出来的活性位点模型，提出了一个机理性假设来解释这一令人困惑的现象。
