Purification and Characterization of Milk Lipase II. Characterization of the Purified Enzyme

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Abstract
The enzymic characteristics of a pure and homogeneous milk lipase were studied. The enzyme was best stored in a frozen state and was extremely unstable at 20, 30, 37, and 45 C. The enzyme exhibited a single pH optimum of 9.0 to 9.2, and its optimum temperature was about 37 C. The enzyme hydrolyzed both milk fat and tributyrin. Evidence has been presented, indicating that the lipolysis of both the substrates is catalyzed by a single enzyme. The enzyme showed little or no activity with ethyl acetate, ethyl decanoate, o-nitrophenyl acetate, and p-nitrophenyl laurate esters in solution, but hydrolyzed the emulsions of milk fat, olive oil, and tributyrin very actively, thus demonstrating the characteristics of a true lipase with a high specificity for glycerol esters. The presence of milk constituents in the reaction mixture seemed to exert an inhibitory effect upon the enzymic activity.
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