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首页> 外文期刊>Catalysis science & technology >Enantioselectivity and catalysis improvements of Pseudomonas cepacia lipase with Tyr and Asp modification
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Enantioselectivity and catalysis improvements of Pseudomonas cepacia lipase with Tyr and Asp modification

机译：通过Tyr和ASP修饰的假单胞菌脂肪酶的对映选择性和催化改善

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摘要

A concise strategy to improve the p-NPP (p-nitrophenyl palmitate) catalytic activity and enantioselectivity towards secondary alcohols of Pseudomonas cepacia lipase (PcL) has been described. The PcL was modified by I-3(-), N-acetyl imidazole (NAI), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC) and ethylenediamine (EDA) in the absence or presence of n-hexane, respectively. After being modified by the four modification reagents, the enantioselectivity (E value) of the PcL towards secondary alcohols was enhanced by 2- to 4-fold. The catalytic activity of EDA-PcL was increased by about 6-fold. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis of modified PcL showed that Tyr(4), Tyr(29), Tyr(45), Tyr(95), Asp(36) and Asp(55) were the modified sites. When Tyr(29) was modified, the E value of PcL towards secondary alcohols was largely improved. MALDI-TOF-MS characterization and molecular dynamics simulation of the lipase indicated that Tyr(29) located inside the catalytic cavity had a significant impact on the E value. The strong steric hindrance of acetyl and iodine ion to the groups on the chiral center of the substrates is responsible for the improvement. In addition, the enhancement of hydrophobicity on the surface of the lipase due to the sidechain replacement of Asp with uncharged hydrophobic groups also improved the E value.
机译：已经描述了一种改善P-NPP（P-硝基苯基）催化活性的简洁策略和对假单胞菌脂肪酶（PCL）继发性醇（PCL）的对映选择性的策略。 PCL通过I-3（ - ），N-乙酰基咪唑（NAI），1-（3-二甲基氨基丙基）-3-乙基钙二二酰胺（EDC）和乙二胺（EDA）分别在N-己烷的情况下分别进行。 。在通过四种修饰试剂进行修饰后，PCL对二次醇的对映选择性（E值）的增强了2至4倍。 EDA-PCL的催化活性增加了约6倍。基质辅助激光解吸/电离飞行时间质谱法（MALDI-TOF-MS）对修饰的PCL分析表明，Tyr（4），Tyr（4），Tyr（29），Tyr（45），Tyr（95），ASP（ASP），ASP（ 36）和ASP（55）是修改的位点。当Tyr（29）修改时，PCL对二次醇的E值在很大程度上得到了改善。脂肪酶的MALDI-TOF-MS表征和分子动力学模拟表明，位于催化腔内的Tyr（29）对E值具有显着影响。乙酰基和碘离子对底物手性中心上的组的强损伤是造成改进的原因。另外，由于ASP替换ASP，脂肪酶表面上疏水性的增强也可以改善E值。

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