The hydrolysis of phosphatidylinositol by lysosomal enzymes of rat liver and brain.
1. Lysosomes from rat liver contain two enzymic systems for hydrolysing phosphatidyl-inositol: a deacylation via lysophosphatidylinositol producing glycerophosphoinositol and non-esterified fatty acid, and a phospholipase C-like cleavage into inositol 1-phosphate and diaclygycerol. 2. The separate enzyme systems involved can be distinguished by gel filtration, differential temperature-stability and the inhibitory action of detergents. 3. The enzyme systems both have pH optima at 4.8 and their attack on a pure phosphatidylinositol substrate is inhibited by many bivalent metals including Ca2+ and Mg2+, and cationic drugs. 4. Whereas the deacylation system will attack other glycerophospholipids, the phospholipase C shows a marked specificity towards phosphatidylinositol, although it will also slowly attach phosphatidylcholine with the liberation of phosphocholine. 5. Gel filtration and temperature-stability distinguish the phospholipase C from lysosomal phosphatidic acid phosphatase, but not from sphingomyelinase. 6. Evidence is presented that an EDTA-insensitive phospholipase C degrading phosphatidylinositol is present in rat brain.
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002412:Cations / Q000494:pharmacology; D002850:Chromatography, Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006868:Hydrolysis; D066298:In Vitro Techniques; D008099:Liver / Q000201:enzymology*; D008247:Lysosomes / Q000201:enzymology*; D010716:Phosphatidylinositols / Q000378:metabolism*; D010740:Phospholipases / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D051381:Rats
D002412:Cations; D004791:Enzyme Inhibitors; D010716:Phosphatidylinositols; D010743:Phospholipids; D010740:Phospholipases