Purification and Characterization of a Novel Lipase from Antarctic Krill

Lipase from Antarctic krill, with a molecular weight of 71.27kDa, 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 Km and Vmax values of 3.27 mmol L-1 and 2.4 Umg-1, respectively, using p-nitrophenyl laurate as the substrate. Li-pase activity was enhanced by adding Ca2+ and Mg2+ ions in the concentration ranges of 0-0.5 mmol L-1 and 0-0.3mmol L-1, respectively, while the activity was inhibited by a further increase in these ion concentrations. Fe3+ and Cu2+ 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.