Properties of phospholipase C isolated from rat liver lysosomes

Phospholipase C (EC 3.1.4.3) has been identified in a soluble, delipidated protein fraction isolated from rat liver lysosomes. Lysosomal phospholipase C is active against all phospholipids tested, including phosphatidylcholine, phosphatidylinositol, phosphatidylglycerol, phosphatidylethanolamine, and phosphatidylserine. It has an acid pH optimum, does not require divalent cations, and is not inhibited by EDTA. With [1-14C]dioleoylphosphatidylcholine as the substrate, 14C-labeled monoglyceride and diglyceride are the reaction products. Monoglyceride is formed rapidly from diglyceride by a lysosomal acid lipase, although some monoglyceride may be formed directly by phospholipase C hydrolysis of lysophosphatidylcholine. The other product, phosphocholine, has been identified by its behavior during Dowex 1-formate anion exchange chromatography. This appears to be the first demonstration in mammalian systems ofa phospholipase C which is active against all phosphoglycerides.