Effects of inorganic phosphorus compounds on the hydrolysis of phosphatidylcholine liposomes by phospholipid-deacylating enzymes.

Structural requirements of inorganic phosphorus compounds as specific activators or inhibitors for phospholipase A2 and phospholipase B were investigated using orthophosphate, pyrophosphate and polyphosphate. It was observed that orthophosphate and pyrophosphate stimulated the activities of phospholipase A2 from bee venom, snake (Naja naja) venom and pig pancreas, and also phospholipase B from the yeast Torulaspora delbrueckii. However, polyphosphate was found to act as an inhibitor for phospholipase A2 in the above species and also for phospholipase B from T. delbrueckii. Orthophosphate and pyrophosphate induced gradual aggregation of liposome, but polyphosphate prolonged the lifetime of the liposome, suggesting that orthophosphate and pyrophosphate destabilize the bilayer structure of phosphatidylcholine and polyphosphate stabilizes it.