Lysosomal lipases of rat liver and kidney.

The subcellular distribution in rat liver and rat kidney of the enzymes hydrolyzing triglycerides at acid pH has been studied. The lipase was shown to be lysosomal by the purification of lysosomes and by the isolation of Triton WR 1339fIlled liver lysosomes. The lipase was found to be bound to the lysosomal membranes, had a pH optimum of 4.2, and required Triton X-160 in the reaction mixture for maximum activity. The lysosomsl lipase had maximum activity against glycerol tridecanoate but had considerable activity against other long chain triglycerides. The lipase was inhibited by NaCl, NaF, iodoacetate, and Hg++ ions and was not affected by Ca++, Mg?+, ethylenediamine tetraacetate, protamine sulfate, and sodium taurocholate. This is the first clear demonstration of a lipase in lysosomes. It is suggested that the lipase is involved in the intralysosomal digestion of triglycerides entering lysosomes by autophagy.