Purification and characterization of a lipase from Pseudomonas aeruginosa KKA-5 and its role in castor oil hydrolysis

An extracellular lipase (triacylglycerol acylhydrolase, EC 3.1.1.3) from Pseudomonas aeruginosa KKA-5 hydrolyzed castor oil by 90%. Purification of this castor oil-hydrolyzing lipase included ammonium sulfate precipitation and successive hydroxylapatite column chromatography. The enzyme was purified 518-fold, It was homogeneous electrophoretically and its molecular weight was estimated to be 30 kDa. The enzyme was stable up to 45 degrees C and retained its activity in the alkaline pH range. Lipase was highly stable in the presence of aqueous organic solvents like methanol and ethanol, It was weakly inhibited in the presence of acetone. The anionic surfactant, sodium dodecyl sulfate, was inhibitory while the cationic surfactants, Triton X-100 and Tween-80 appreciably enhanced activity. Lipase was stabilized significantly by Ca2+, Inactivation of the enzyme by EDTA was overcome by sequential CaCl2 treatment, This finding suggests the existence of a calcium-binding site in Pseudomonas aeruginosa KKA-5 lipase.