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.
Highlights
The pH profile obtained for enzymes in rat liver homog- ylene polymer) was from Ruger Chemical Company, Inc. (Irvingenate which hydrolyze glycerol estersof decanoic acid shows ton-on-Hudson, New York)
Occurrence and Localization of Glyceride-hydrolyzi Systems in Rat Liver-Fig. 1A illustrates that rat liver homogenates exhibit two different lipolytic activities, one with optimum activity at pH 5 and the other at pH 8.8 to 9.0
With glycerol tridecanoate as substrate, the specific activity at acid pH was more than twice that exhibited at the alkaline pH optimum
Summary
The pH profile obtained for enzymes in rat liver homog- ylene polymer) was from Ruger Chemical Company, Inc. (Irvingenate which hydrolyze glycerol estersof decanoic acid shows ton-on-Hudson, New York). When soluble lysosomal lipase hydrolyzed glycerol tri(oleate-1-14C), the percentage of radioactivity recovered in the products was as follows: cals. A comparison of lipase activity in liver lysosomeswith that in Triton WR 1339-filledliver lysosomes, as well as the limitations imposedby the use of Triton-filled from Boots Pure Drug Company, Ltd., Nottingham, England, and sodium diethyldithiocarbamate was obtained from Eastman. Glycerol 1-monodecanoate and glycerol 1-monooleate were synthesized from 1,2-isopropylideneglycerol(2,2-dimethyl-l , 3-dioxolanel-methanol) by the method of Hartman [10] as modified by Anfinsen and Perkins (1 l), except that the final cystallization and Lysosomes of rat liver and kidney and of rabbit polymorpho- further recrystallizaticns were carried out with 10 volumes of penuclear leukocytes [1, 2] have various lipolytic activities toward troleum ether (b.p. 30-60”).
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