Improving the catalytic activity of lipase LipK107 from Proteus sp. by site-directed mutagenesis in the lid domain based on computer simulation

The capacity of lipase LipK107 from Proteus sp. catalyzing the kinetic resolution of racemates was investigated. The resolution of racemic 1-phenylethanol in organic medium was selected as model reaction. The conversion was dramatically dependent on the water content and the LipK107 showed high activity in a wide range of water content without appreciable loss of enzyme enantiodiscrimination. Besides, the chain length of acyl donor also had a significant effect on the conversion, and the highest enantioselectivity was achieved when methyl palmitate was used. Based on the analysis of computer model structure of LipK107, different mutations were introduced into the lid region. Each derivative of LipK107 was expressed, purified, and assessed of the activity. According to the prediction, using mutants E130L + K131I and T138V as catalyst, respectively, the conversions of 1-phenylethanol improved greatly with a slight increase of enantiodiscrimination. In addition, the effects of hydrophobicity and electrostatic of the lid on lipase activity were determined. This work indicated that the modification of the lid might considerably enhance the activity and improve the yield of catalytic reactions, which could apply to other lipases. The computer simulations would make the process of identifying amino acids for substitution efficiently.