The Lipolytic Activity of Human Milk

Abstract The lipolytic activity of human skimmed milk is studied with respect to pH, temperature, substrate nature and concentration and in the presence of various chemicals added to the assay medium. The enzymatic hydrolysis is maximum at pH 8 and 37° C in an emulsion of tributyrin 5 mM and in the presence of sodium taurocholate. Tributyrin is also hydrolyzed but about 15 times more slowly in the absence of this bile salt. Lipolysis of triolein does not proceed unless sodium taurocholate is added to the medium at a concentrations greater than 0.5 mM. In 10 mM sodium taurocholate, the reaction rates are approximately 7.5 and 0.5 units per mg of proteins for tributyrin and triolein, respectively. The hydrolysis of tributyrin and triacetin at concentrations below saturation is enhanced by the presence of low concentrations of NaCl, suggesting that the catalytic process depends on the presence of a substrate in the micellar form, i.e. on the action of an interfacial enzyme.