Hydrolysis of phospholipids by phospholipase A2 in intact membranes of sheep erythrocytes.
We can detect phospholipase A activity in non-hemolyzed sheep erythrocytes, using dilauroylglycerophosphocholine as an exogenous substrate. Only substrates such as dilauroylglycerophosphocholine, which can be incorporated into membranes, could be hydrolyzed by the enzyme, egg phosphatidylcholine being only slightly sensitive to the enzyme in the absence of detergent. Egg phosphatidylcholine is not hydrolyzed even in the presence of dilauroylglycerophosphocholine at the concentration used routinely in the present experiment, indicating that dilauroylglycerophosphocholine itself does not behave as a detergent under the present experimental conditions. Exogenous calcium ions are necessary for the activity, but it was abolished by EDTA. This finding suggests that the Ca2+ binding site of the enzyme may be exposed on the outer surface of the erythrocyte membrane.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000201:enzymology*; D007700:Kinetics; D008563:Membrane Lipids / Q000097:blood*; D010740:Phospholipases / Q000097:blood*; D010741:Phospholipases A / Q000097:blood*; D054467:Phospholipases A2; D010743:Phospholipids / Q000097:blood*; D012756:Sheep
D008563:Membrane Lipids; D010743:Phospholipids; D004492:Edetic Acid; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium