Specificity and Other Properties of Lysosomal Lipase of Rat Liver

The pH profile obtained for enzymes in rat liver homogenate which hydrolyze glycerol esters of decanoic acid shows two distinct peaks of activity, one at pH 5 to 5.2 and the other at pH 8.6 to 9.8, where Lysosomal lipase is strongly inhibited by certain sulfhydryl reagents.

Abstract

Abstract The pH profile obtained for enzymes in rat liver homogenate which hydrolyze glycerol esters of decanoic acid shows two distinct peaks of activity, one at pH 5 to 5.2 and the other at pH 8.6 to 9. The activity at acid pH is associated with lysosomes, and that at alkaline pH with microsomes. Glycerol tri-, 1,2-di-, and 1-monodecanoate are hydrolyzed by lysosomes in decreasing order of activity, and by microsomes in increasing order of activity. When soluble lysosomal lipase hydrolyzed glycerol tri(oleate-1-14C), the percentage of radioactivity recovered in the products was as follows: oleic acid, 40%; glycerol 1,2-dioleate, 52%; glycerol 1,3-dioleate, 8%; and glycerol monooleate, 0%. Complete solubilization of lysosomal lipase is achieved by suspending the lysosomal pellet in 0.05 m sodium phosphate buffer, pH 6.8. Lysosomal lipase is strongly inhibited by certain sulfhydryl reagents. A comparison of lipase activity in liver lysosomes with that in Triton WR 1339-filled liver lysosomes, as well as the limitations imposed by the use of Triton-filled lysosomes, is discussed.