(1) The hydrolysis of 32P- or myo-[2-3H]inositol-labelled rat liver microsomal phospholipids by rat liver lysosomal enzymes has been studied. (2) The relative rates of hydrolysis of phospholipids at pH4.5 are: sphingomyelin>phosphatidylethanolamine>phosphatidylcholine> phosphatidylinositol. (3) The predominant products of phosphatidylcholine and phosphatidylethanolamine hydrolysis are their corresponding lyso-compounds, indicating a slow rate of total deacylation. (4) Ca2+ inhibits the hydrolysis of all phospholipids, though only appreciably at high (>5mm) concentration. The hydrolysis of sphingomyelin is considerably less sensitive to Ca2+ than that of glycerophospholipids. (5) Analysis of the water-soluble products of phosphatidylinositol hydrolysis (by using myo-[3H]inositol-labelled microsomal fraction as a substrate) produced evidence that more than 95% of the product is phosphoinositol, which was derived by direct cleavage from phosphatidylinositol, rather than by hydrolysis of glycerophosphoinositol. (6) This production of phosphoinositol, allied with negligible lysophosphatidylinositol formation and a detectable accumulation of diacylglycerol, indicates that lysosomes hydrolyse membrane phosphatidylinositol almost exclusively in a phospholipase C-like manner. (7) Comparisons are drawn between the hydrolysis by lysosomal enzymes of membrane substrates and that of pure phospholipid substrates, and also the possible role of phosphatidylinositol-specific lysosomal phospholipase C in cellular phosphatidylinositol catabolism is discussed.
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Research Article|
August 15 1979
Hydrolysis of membrane phospholipids by phospholipases of rat liver lysosomes
Donald E. Richards;
Donald E. Richards
1Department of Biochemistry, A.R.C. Institute of Animal Physiology, Babraham, Cambridge CB2 4AT, U.K.
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Robin F. Irvine;
Robin F. Irvine
1Department of Biochemistry, A.R.C. Institute of Animal Physiology, Babraham, Cambridge CB2 4AT, U.K.
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Rex M. C. Dawson
Rex M. C. Dawson
1Department of Biochemistry, A.R.C. Institute of Animal Physiology, Babraham, Cambridge CB2 4AT, U.K.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1979 London: The Biochemical Society
1979
Biochem J (1979) 182 (2): 599–606.
Citation
Donald E. Richards, Robin F. Irvine, Rex M. C. Dawson; Hydrolysis of membrane phospholipids by phospholipases of rat liver lysosomes. Biochem J 15 August 1979; 182 (2): 599–606. doi: https://doi.org/10.1042/bj1820599
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