文献类型：期刊文献

英文题名：Investigating pH and Cu (II) effects on lipase activity and enantioselectivity via kinetic and spectroscopic methods

作者：Xu, Tian-Wen[1]; Xu, Jian-He[1]; Yu, Wei[2]; Zhong, Ju-Hua[3]

机构：[1] Laboratory of Biocatalysis and Bioprocessing, State Key Laboratory of Bioreactor Engineering, Shanghai, China; [2] Key Laboratory for Ultrafine Materials of Ministry of Education, Shanghai, China; [3] Department of Physics, East China University of Science and Technology, Shanghai, China

年份：2006

卷号：1

期号：11

起止页码：1293

外文期刊名：Biotechnology Journal

收录：MEDLINE(收录号：17068757);;EI(收录号：20122215075781);PubMed

语种：英文

外文关键词：Yeast - Candida - Free energy - Catalysis - Emission spectroscopy - Enzyme activity - Activation energy - Copper compounds - Enantioselectivity - pH effects

摘要：For Candida rugosa lipase (CRL) catalyzed hydrolysis of racemic 1-phenethyl acetate, both the weakly acidic pH (pH 6.0) and the addition of 1 mM copper (II) ion enhanced the enzyme activity and enantioselectivity (E value) about twofold, as compared with that under neutral pH and noadditive conditions. The decrease of activation free energy (ΔG) and increase of kcat(R)/kcat(S) at weakly acidic pH and/or in the presence of copper (II) characterized the kinetic behavior of CRL. On the other hand, for providing reasonable insights into the catalytic mechanism and the structural basis for enantioselectivity alteration, spectroscopic techniques were employed to probe conformational changes of the enzyme in each medium assayed. The fluorescence emission spectra revealed that pH and copper (II) might exert different effects on the microenvironment of Trp residue and thereby on the protein conformation, which could be further verified by UV-visible and Raman spectra. The conformational modulation of CRL associated with either pH or copper (II) concentration in the reaction medium could be attributed to the flexible and sensitive conformation of the enzyme, which is responsible for the significant variation of apparent activity and enantioselectivity with the tuning of biocatalyst microenvironment. ? 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.