The catabolism of phosphatidylinisitol by an EDTA-insensitive phospholipase A1 and calcium-dependent phosphatidylinositol phosphodiesterase in rat brain.
1. A rat brain supernatant and microsomal fraction contained a phospholipase A1 enzyme which hydrolysed phosphatidylinositol at pH 8 in the absence of calcium. Triolein and phosphatidylcholine were not attacked under the same incubation conditions. 2. No evidence could be obtained for a phospholipase A2 in the microsomal preparation, and in the presence of Ca2+ the release of fatty acid observed was due to phosphatidylinositol phosphodiesterase followed by diacylglycerol lipase action. 3. Brain phosphatidylinositol phosphodiesterase showed extensive activity in the alkaline range (7-8.5) as well as at pH 5-5.5. The activity at higher pH values required higher calcium concentrations and disappeared on purification of the soluble enzyme by ammonium sulphate fractionation. 4. In general the ratio between inositol 1,2-(cyclic)phosphate and inositol 1-phosphate produced by phosphodiesterase action decreased with increasing pH.
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism*; D004492:Edetic Acid / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010716:Phosphatidylinositols / Q000378:metabolism*; D010740:Phospholipases / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism*; D054466:Phospholipases A1; D054467:Phospholipases A2; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D051381:Rats
D005227:Fatty Acids; D010716:Phosphatidylinositols; D004492:Edetic Acid; D010740:Phospholipases; D010741:Phospholipases A; D054466:Phospholipases A1; D054467:Phospholipases A2; D010727:Phosphoric Diester Hydrolases; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D008274:Magnesium; D002118:Calcium