Penicillium abeanum lipase was purified to homogeneity as judged by non-denaturing and denaturing polyacrylamide gel electrophoresis. The enzyme is a monomeric protein with a molecular mass of approximately 28 kDa and a pI of 3.4. The optimal pH at 25 degrees C and the optimal temperature at pH 7.5 were 7-8, and 25-30 degrees C, respectively. The enzyme hydrolyzes the 1- and 3-position ester bonds at nearly nine times the rate of cleavage at the 2-position. The enzyme showed lower activities towards ester bonds of polyunsaturated fatty acids as compared with those of other acids, and was proved effective for increasing the concentration of docosahexaenoic acid (22:6) in tuna oil.