Bigley Andrew N, Narindoshvili Tamari, Xiang Dao Feng, Raushel Frank M
Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States.
Biochemistry. 2018 Mar 27;57(12):1842-1846. doi: 10.1021/acs.biochem.8b00145. Epub 2018 Mar 13.
The phosphotriesterase from Sphingobium sp. TCM1 ( Sb-PTE) is notable for its ability to hydrolyze organophosphates that are not substrates for other enzymes. In an attempt to determine the catalytic properties of Sb-PTE for hydrolysis of chiral phosphotriesters, we discovered that multiple phosphodiester products are formed from a single substrate. For example, Sb-PTE catalyzes the hydrolysis of the R-enantiomer of methyl cyclohexyl p-nitrophenyl phosphate with exclusive formation of methyl cyclohexyl phosphate. However, the enzyme catalyzes hydrolysis of the S-enantiomer of this substrate to an equal mixture of methyl cyclohexyl phosphate and cyclohexyl p-nitrophenyl phosphate products. The ability of this enzyme to catalyze the hydrolysis of a methyl ester at the same rate as the hydrolysis of a p-nitrophenyl ester contained within the same substrate is remarkable. The overall scope of the stereoselective properties of this enzyme is addressed with a library of chiral and prochiral substrates.
鞘氨醇单胞菌属菌株TCM1（Sb-PTE）中的磷酸三酯酶以其水解其他酶无法作用的有机磷酸酯的能力而著称。为了确定Sb-PTE对手性磷酸三酯水解的催化特性，我们发现单一底物会形成多种磷酸二酯产物。例如，Sb-PTE催化磷酸甲基环己基对硝基苯酯的R-对映体水解，专一性生成甲基环己基磷酸酯。然而，该酶催化此底物的S-对映体水解，生成甲基环己基磷酸酯和环己基对硝基苯磷酸酯产物的等量混合物。这种酶以与同一底物中对硝基苯酯水解相同的速率催化甲酯水解的能力非常显著。我们使用一系列手性和前手性底物研究了该酶立体选择性特性的整体范围。
