Studies on the substrate specificity of purified human milk lipoprotein lipase

The fatty acid specificity of purified human milk lipoprotein lipase was studied using the C₁₈ to C₅₄ (total acyl carbon number) saturated and the C₅₄ mono-, di- and triunsaturated monoacid triacylglycerols. Kinetic determinations indicated that the medium-chain triacylglycerols were better substrates than long- or very short-chain saturated triacylglycerols. The unsaturated triacylglycerols were hydrolyzed at rates comparable to that of tricaprylin with triolein having the highest rate of hydrolysis of the unsaturated species tested. The enzyme attacked the primary ester bond much more readily than the secondary ester bond. The purified human milk lipoprotein lipase showed a preferential stereospecific lipolysis of thesn-1-position of the triacylglycerol molecule.