A novel enantioselective lipase from Acinetobacter sp. ES-1 exhibiting an excellent enantioselectivity for (S)-ketoprofen ethyl ester was purified to homogeneity using hydrophobic interaction chromatography. The molecular weight and pI value of the purified enantioselective lipase were 32 kDa and 6.2, respectively, and the optimal temperature and pH were 40 degrees C and 7.0. The activity was enhanced 1.5-fold in the presence of Ca2+ ions, and showed the substrate specificity preferably for a medium-chain length, such as triacylglycerides and p-nitrophenyl esters. The N-terminal amino acid residue was A-V-R-S-I-D-G-L-A-I-N-Q-S-A, and no homology was found among other known lipases, indicating a novel type enzyme. The enantioselective hydrolysis of (R,S)-ketoprofen ethyl ester to optically pure (S)-ketoprofen was carried out in the aqueous phase reaction system achieving an high enantiomeric excess of 0.99 and conversion yield of 0.49 after 72 h. (c) 2005 Elsevier Inc. All rights reserved.