Majumder Abir B, Shah Shweta, Gupta Munishwar N
Chemistry Department, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India.
Chem Cent J. 2007 Apr 18;1:10. doi: 10.1186/1752-153X-1-10.
Use of enzymes in low water media is now widely used for synthesis and kinetic resolution of organic compounds. The frequently used enzyme form is the freeze-dried powders. It has been shown earlier that removal of water molecules from enzyme by rinsing with n-propanol gives preparation (PREP) which show higher activity in low water media. The present work evaluates PREP of the lipase (from Rhizomucor miehei) for kinetic resolution of (R,S)-beta-citronellol. The acylating agent was vinyl acetate and the reaction was carried out in solvent free media.
The PREP, with 0.75% (v/v, reaction media) water, was indeed found to be more efficient and gave 95% conversion to the ester. Using this PREP, with no added water, 90% ee for (R)-(+)-beta-citronellyl acetate at 45% conversion (E = 42) was obtained in 4 h. The control with freeze-dried enzyme, with zero water content, gave 78% ee at 30% conversion (E = 13). FT-IR analysis showed that PREP had retained the alpha-helical content of the enzyme. On the other hand, freeze-dried enzyme showed considerable loss in the alpha-helical content.
The results show that PREP may be a superior biocatalyst for enantioselective conversion by enzymes in low-water media.
酶在低水介质中的应用现已广泛用于有机化合物的合成和动力学拆分。常用的酶形式是冻干粉末。早期研究表明，用正丙醇冲洗酶以去除水分子可得到在低水介质中表现出更高活性的制剂（PREP）。本工作评估了用于（R，S）-β-香茅醇动力学拆分的脂肪酶（来自米黑根毛霉）的PREP。酰化剂为乙酸乙烯酯，反应在无溶剂介质中进行。
确实发现含水量为0.75%（v/v，反应介质）的PREP效率更高，酯转化率达95%。使用这种未添加水的PREP，在4小时内，（R）-（+）-β-香茅醇乙酸酯在转化率为45%时对映体过量值（ee）为90%（E = 42）。含水量为零的冻干酶对照在转化率为30%时ee值为78%（E = 13）。傅里叶变换红外光谱（FT-IR）分析表明，PREP保留了酶的α-螺旋含量。另一方面，冻干酶的α-螺旋含量有相当大的损失。
结果表明，PREP可能是低水介质中酶对映选择性转化的优良生物催化剂。
