Dynamics of formation of lysoforms on enzymatic hydrolysis of phosphatidylalkanols

Hydrolysis of 1,2-dioleoyl-sn-glycero-3-phosphomethanol (DOPM), 1,2-dioleoyl-sn-glycero-3-phosphoethanol (DOPEt), 1,2-dioleoyl-sn-glycero-3-phosphoethyleneglycol (DOPEG), and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) catalyzed by phospholipase A₂ (PLA₂) from porcine pancreas was studied in single-component and binary model bilayer membranes (liposomes). The presence of anionic phosphatidylalkanols increases the rate of hydrolysis of zwitterionic DOPC in liposomes by the action of PLA₂. The rate of formation of lysoforms of anionic (acidic) lipids at the initial reaction stage in single-component liposomes increased in the following sequence: DOPEG < DOPM < DOPEt (compared with that for the zwitterionic DOPC). In binary liposomes formation of lyso-DOPC increased in the presence of acidic lipids in the following sequence: DOPM < DOPEt < DOPEG. This indicates that the size of polar fragment of the second substrate and the presence of free hydroxy groups in the head of DOPEG may possibly activate DOPC hydrolysis by the action of PLA₂ in the presence of anionic phospholipids including cardiolipin; the studied phospholipids model fragments of the latter.