摘要
考察了反应条件对不动杆菌Acinetobactersp .YQ2 31催化外消旋环戊酮醇乙酸酯对映选择性水解的反应速度和对映选择性的影响 .确定的最佳酶反应条件为 pH 8 0 ,温度 5 0℃ .不同乳化剂对对映选择性的影响不同 ,以壬基酚聚氧乙烯醚的效果最好 ,当其加入量为 15 g/L 时 ,反应的对映选择性最高 .产物环戊酮醇对酶活性有显著的抑制作用 .细胞中的酯酶优先水解 (R) 环戊酮醇乙酸酯 ,生成 (R) 环戊酮醇 ,在底物浓度为 2 5 0mmol/L时 ,对映体比率 (E值 )可达 5 0 .
The effects of reaction conditions on the reaction rate and selectivity of the enantioselective hydrolysis of racemic 4-hydroxy-3-methyl-2-(2-propenyl)-cyclopent-2-enone (HMPC) acetate by Acinetobacter sp. strain YQ231 were investigated. The apparent activity of the resting cells increases with pH up to 11.0, but the non-selective simultaneous hydrolysis of the chiral ester becomes significant at pH>9.0. Therefore, to prevent possible non-enzymatic hydrolysis of the ester and possible racemization of the product, the enzymatic resolution is carried out at pH 8.0. When the cells are preserved in buffers at pH ranging from 9.0 to 10.5 for 12 h, the residual activity of the resting cells increases. This is attributed to the possible permeabilizing effect on the cell membrane, which facilitates the trans-membrane transport of substrates and products. The highest activity of the cells is observed at 50 ℃, and the best stability at 30 ℃. Nonyl phenol polyethyleneoxy ether is the most suitable emulsifier for the substrate and its optimal concentration is 15 g/L in regarding to the enantioselectivity of the esterase-catalyzed reaction. The enzymatic reaction is inhibited by the product HMPC, but not by the substrate HMPC acetate up to 1.0 mol/L. The esterase in the resting cells preferentially hydrolyzes the (R)-enantiomer of the racemic ester, producing enantiopure (R)-HMPC. The enantiomeric ratio (E-value) is 50 in the case of 250 mmol/L substrate.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2003年第8期613-618,共6页
基金
国家自然科学基金资助项目 (2 0 176 0 11)
关键词
环戊酮醇乙酸酯
对映选择性水解
环戊酮醇
酶促拆分
微生物酯酶
不动杆菌
cyclopentenolone acetate, enantioselective hydrolysis, cyclopentenolone, enzymatic resolution, microbial esterase, Acinetobacter sp.
