Determination of amino acids and dipeptides is correlated significantly with optimum temperatures of microbial lipases
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ORIGINAL ARTICLE
Determination of amino acids and dipeptides is correlated significantly with optimum temperatures of microbial lipases Hui-Min Zhang & Jian-Fang Li & Min-Chen Wu & Hong-Ling Shi & Cun-Duo Tang
Received: 16 March 2012 / Accepted: 20 April 2012 # Springer-Verlag and the University of Milan 2012
Abstract Amino acids and dipeptides that are correlated significantly with lipase optimum temperatures were searched for in 34 microbial lipase sequences by a stepwise regression method. The positive dipeptides were found to be IR, KS, NY, SA, ST and YR, whereas negative ones were DK, DY, IS, KA, WS, YS and QI. The calculated optimum temperatures from an optimal regression equation of dipeptides fitted the corresponding experimental optimum temperatures of lipases very well, and the maximal absolute difference was only 3.43°C. The spatial positions of the related dipeptides were searched for in two known crystal structures of a thermophilic and mesophilic lipase, respectively. Most of the positive dipeptides were sited in the α-helices, while the negative ones were located mainly in the β-strands or coils and about half of them existed in the N- or C-terminii of the lipases. The results obtained will be very useful in lipase engineering for enhancing lipase thermostability. Keywords Microbial lipase . Dipeptide . Optimum temperature . Stepwise regression method . Thermostability H.-M. Zhang : J.-F. Li School of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, People’s Republic of China M.-C. Wu (*) : H.-L. Shi School of Medicine and Pharmaceutics, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, People’s Republic of China e-mail: [email protected] C.-D. Tang The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, People’s Republic of China
Introduction Lipases (triacylglycerol acylhydrolases, EC 3.1.1.3) are enzymes that catalyze the hydrolysis of triacylglycerols, as well as the synthesis of lipids, esterification and transesterification (Akoh et al. 2004; Klibanov 2001). Lipase enzymes are distributed widely in animals, plants and microorganisms, among which microbial lipases have attracted special attention for various industrial applications because most microbial lipases can be extracellularly produced by fermentation in large quantities and have broad substrate specificity (Sharma et al. 2002). Microbial lipases have been applied in many industries, such as detergents, foods, pharmaceuticals and cosmetics (Nelofer et al. 2011). However, industrial bioprocesses must very often be performed at a high temperature, which limits the usage of lipases. Therefore, protein engineering technology by means of site-directed mutagenesis (Han et al. 2009), directed evolution (Gatti-Lafranconi et al. 2008) and computational design (Vieille and Zeikus 2001) has been performed to enhance lipase thermostability. To understand the thermostable mechanism, methods such as compar
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