Purification and Characterization of a Novel Lipase from Antarctic Krill

Abstract

Lipase from Antarctic krill, with a molecular weight of 71.27 kDa, was purified with ammonium sulfate precipitation and a series of chromatographic separations over ion exchange (DEAE) and gel filtration columns (Sephacryl S-100), resulting in 5.2% recovery with a 22.4-fold purification ratio. The optimal pH and temperature for enzyme activity were 8.0 and 45°C, respectively. Purified lipase had K _m and V _max values of 3.27 mmol L ⁻¹ and 2.4 U mg ⁻¹, respectively, using p-nitrophenyl laurate as the substrate. Lipase activity was enhanced by adding Ca ²⁺ and Mg ²⁺ ions in the concentration ranges of 0–0.5 mmol L ⁻¹ and 0–0.3 mmol L ⁻¹, respectively, while the activity was inhibited by a further increase in these ion concentrations. Fe ³⁺ and Cu ²⁺ ions showed obvious inhibitory effects on enzyme activity, and the inhibition rates were 71.8% and 53.3% when the ion concentrations were 0.5 mmol L ⁻¹.