Identification, molecular cloning and expression of a new esterase from Pseudomonas sp. KCTC 10122BP with enantioselectivity towards racemic ketoprofen ethyl ester

A newly isolated gene from Pseudomonas sp. KCTC 10122BP, encoding an esterase with enantioselectivity towards racemic ketoprofen (rac-ketoprofen) ethyl ester, was cloned in Escherichia coli and its nucleotide sequence determined. The deduced amino acid sequence predicted an open reading frame (ORF) encoding a polypeptide of 381 amino acid residues (1143 nucleotides) with a calculated isoelectric point of pH 5.32 and molecular mass of 41,149 Da. The primary structure of the enzyme exhibited a significant level of homology (>31%) with those of related enzymes from various sources and an extreme homology (>81%) with five esterases from the genus Pseudomonas. The enzyme was expressed at a high level in an active form in the soluble fraction and purified to homogeneity by a successive chromatographic procedure. The purified enzyme was determined to be a monomer, plus it exhibited a strict selectivity (>99%) and high activity (2360 units/mg-protein) towards (S)-ketoprofen ethyl ester.