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Endogenous lipolytic activities during autolysis of highly enriched hepatic lysosomes
Author(s) -
Beckman Jeffrey K.,
Owens Kenneth,
Weglicki William B.
Publication year - 1981
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02535031
Subject(s) - lysophosphatidylethanolamine , phosphatidylinositol , phosphatidylethanolamine , biochemistry , autolysis (biology) , lysophosphatidylcholine , sphingomyelin , phosphatidylcholine , incubation , chemistry , lipase , phospholipase , ceramide , phospholipase c , phospholipase a1 , fatty acid , clinical chemistry , enzyme , phospholipid , membrane , apoptosis , kinase
Highly enriched (50‐ to 70‐fold) fractions of “native” lysosomes were isolated using continuous flow electrophoresis from livers of rats which had not been pretreated with Triton WR‐1339. Incubation of lysosomes for 30 min at pH 5.0 in the presence of 5 mM EDTA resulted in a dramatic loss in the content of fatty acids bound to triacylglycerols (137 down to 10 μmol/mg protein) and to phospholipids and an elevation in the level of unesterified fatty acid. Phosphatidylcholine, phosphatidylethanolamine and sphingomyelin concentrations decreased whereas those of lysophosphatidylethanolamine (0.8 up to 8.5% of total lipid‐P) and lysophosphatidylcholine (1.9 up to 16.7%) rose in a manner parallel to their respective, fully acylated lipids. Other phospholipids, including phosphatidylinositol, did not change in concentration during incubation. These results indicate that lysosomal phospholipase A, sphingomyelin and triacylglycerol lipase are activated by incubation at acid pH, enabling them to hydrolyze endogenous lysosomal lipids. However, lysosomal phosphatidylinositol‐directed phospholipase C is apparently unable to interact with phosphatidylinositol of the lysosomal membrane.