Lytic and non-lytic degradation of phospholipids in mammalian erythrocytes by pure phospholipases

Abstract

1. 1. Sphingomyclinase (sphingomyelin cholinephosphohydrolase) from Staphylococcus aureus hydrolysed 75–80% of the sphingomyelin in human and pig erythrocytes and 50–60% of the sphingomyelin in ox and sheep erythrocytes, without producing haemolysis of the cells. 2. 2. Although phospholipase C (phosphatidylcholine cholinephosphohydrolase, EC 3.1.4.3) from Bacillus cereus alone was not lytic, the combination of sphingomyelinase and phospholipase C produced haemolysis of human and pig erythrocytes and extensive degradation of all the phospholipid classes in the ghosts thus produced. In contrast, the combination of these two enzymes failed to produce lysis of ox and sheep erythrocytes; in these cells the only phospholipid degraded was sphingomyelin. 3. 3. Human erythrocytes treated with sphingomyelinase showed increased osmotic fragility relative to control cells. 4. 4. In the intact erythrocytes studied, phosphoglyceride molecules are not accessible to phospholipases A 2 and C. Removal of choline phosphate residues from sphingomyelin exposes the phosphoglycerides to phospholipases A 2 and C in human and pig erhythrocytes but not in ox and sheep red cells.