类红球细菌羧酸酯酶催化1-苯乙醇的转酯反应研究

The Study of Transesterification Catalyzed by Rhodobacter Sphaeroides Esterase

以来源于类红球细菌(Rhodobacter sphaeroides)的羧酸酯酶RspE为催化剂,首次探讨了它在有机溶剂中的催化特性,并在研究中将1-苯乙醇与乙酸乙烯酯的转酯反应作为模型反应。比较5种不同有机溶剂以及4个不同温度对酯酶RspE催化反应的影响,发现在45oC乙腈作为溶剂时酶的催化活性最高。而在酶的稳定性研究中,发现酯酶RspE在有机溶剂中暴露4天后,催化转酯反应进行两天的保留活性为58.3%,表明有机溶剂中的长时间暴露使得酯酶的催化活性有损失。在最适条件下反应6天后的结果显示,转化率达到了47.9%,而对映体选择性值达到了64,表明该羧酸酯酶对1-R-苯乙醇具有良好的手性选择性。经本实验研究发现,类红球细菌羧酸酯酶RspE在有机溶剂中能够有选择性地催化1-苯乙醇转酯反应的进行,表明该酯酶不但可以在水相中催化水解反应的进行,还可以作为一种新的生物催化剂应用于有机相催化工业。

In this study, a carboxyl esterase from Rhodobacter sphaeroides was introduced as a catalyst in organic solvent, and the transesterification of 1-phenethyl alcohol and vinyl acetate was served as a model reaction. It was found that changes in used solvent and temperature influence the activity of the esterase and it was observed that the highest activity was obtained when acetonitrile was served as the solvent with the catalytic temperature of 45℃. However, after four days＇ exposure in organic solvent, the relative activity of the esterase decreases to 58.3%, which indicates that the esterase is partially denatured due to the toxicity of organic solvent. Six days＇ reaction carried out in optimal condition shows that the molar conversation reaches to 47.9% and the E value is 64. It demonstrated that this carboxyl esterase displays high enantioselectivity toward R-1-phenetyl alcohol and can be applied to industrial manufacturing as a novel biocatalyst.