Cloning, expression, purification and characterization of the carboxylesterase Yeig from Escherichia coli k12

In this work, enzyme YeiG from Escherichia coli K12-MG1655 which has no definitely known biochemical function has been cloned, expressed, purified and characterized. Alignment studies show that YeiG has an alpha/beta-hydrolase fold with catalytic triad formed by Ser145, Asp223 and His256 at active sites and Ser145 is located in the conserved motif Gly-Xaa-Ser-Xaa-Gly. Enzyme assays demonstrate that YeiG has a significant carboxylesterase activity, low enzymatic activities for lipase and epoxide hydrolase and no detectable enzymatic activities for other enzymes selected in our study. Towards the hydrolysis of p-nitrophenyl esters of fatty acids, YeiG possesses broad substrate specificity with a preference for short acyl chain esters, and has maximum activity towards C4 ester. The integrating bioinformatics and enzyme assays have suggested that YeiG from E. coli K12-MG1655 should be a carboxylesterase.