The purification and characterization of a lipase produced by Pseudomonas aeruginosa strain MB 5001 that was selected for its unique bioconversion properties is described herein. The purified lipase bioconverts dimethyl 5-(3-(2-(7-chloroquinolin-2-yl)-ethyl)phenyl)4, 6-dithianonanedioate (diester) to its (S)-ester acid, an intermediate in the synthesis of Verlukast, a leukotriene receptor antagonist. In its native form, the enzyme exists as high-molecular-weight aggregates that are dissociated with Triton X-100. The purified enzyme has a molecular weight of 29,000 daltons, a pH optimum of 8.0, a temperature optimum of 55-degrees-C, and is stable for 1 h at 40-degrees-C. This lipase is strongly inhibited by 1 mm ZnSO4 (94% inhibition) but is stimulated by the addition of 10 mm CaCl2 (1.24-fold) and 200 mm taurocholic acid (1.6-fold). It is more active on short-chain versus long-chain triglycerides, and hydrolyzes C18-unsaturated fatty acid esters more efficiently than it hydrolyzes C18-saturated fatty acid esters. In light of its catalytic and physicochemical properties, this enzyme is regarded as a novel lipase.