标题：Theoretical studies on the common catalytic mechanism of transketolase by using simplified models
作者：Sheng, Xiang; Liu, Yongjun; Liu, Chengbu
作者机构：[Sheng, Xiang; Liu, Yongjun; Liu, Chengbu] Shandong Univ, Sch Chem & Chem Engn, Jinan 250100, Shandong, Peoples R China.; [Liu, Yongjun] Chinese Aca 更多
通讯作者地址：[Liu, YJ]Shandong Univ, Sch Chem & Chem Engn, Jinan 250100, Shandong, Peoples R China.
来源：JOURNAL OF MOLECULAR GRAPHICS & MODELLING
关键词：Transketolase; Density functional theory (DFT) method; Reaction; mechanism; ThDP-dependent enzyme; 2-Carbon fragment transfer
摘要：Transketolase is a convenient model system to study enzymatic thiamin catalysis. By using density functional theory (DFT) method, the transfer mechanism of a 2-carbon fragment between a donor ketose X5P and an acceptor aldose R5P catalyzed by transketolase has been studied on simplified models. The calculation results indicate that the whole reaction cycle contains several proton transfer processes as well as C-C bond formation and cleavage steps. Each C-C bond formation or cleavage step is always accompanied by a proton transfer process, which follows a concerted but asynchronous mechanism. The C-C bond formation is always prior to the proton transfer, and the C-C bond cleavage is always later than proton transfer, suggesting that the C-C bond ligation facilitates the proton transfer, and proton transfer promotes the C-C bond cleavage. In the first half- and second half-reactions, the energy barriers of C-C bond formations are always higher than those of C-C bond cleavages. The 4-amino group of cofactor ThDP and histidine residue can act as the proton donor/acceptor during the catalytic reaction. (C) 2012 Elsevier Inc. All rights reserved.