ABSTRACT
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.
Subject(s)
Alcohols/chemistry , Liposomes/chemistry , Phosphatidic Acids/chemistry , Phospholipases A/metabolism , Alcohols/metabolism , Animals , Ions , Lipolysis , Pancreas/enzymology , Phosphatidic Acids/metabolism , Phospholipases A2 , Structure-Activity Relationship , Substrate Specificity , Swine , Time FactorsABSTRACT
Hydrolysis of dioleoylphosphatidylethanol (DOPEt) and dioleoylphosphatidylcholine (DOPC) catalyzed by phospholipase A2 (PLA2) from porcine pancreas has been studied in single-component and binary liposomes in the absence and in the presence of ethanol. DOPEt (an anionic phospholipid) was found to increase the rate of hydrolysis of zwitterionic DOPC in liposomes under the action of PLA2.
Subject(s)
Ethanol/pharmacology , Glycerophospholipids/pharmacology , Pancreas/drug effects , Phospholipases A/metabolism , Animals , Calorimetry , Enzyme Activation , Hydrolysis , Kinetics , Pancreas/enzymology , Phosphatidylcholines/metabolism , Phospholipases A2 , SwineABSTRACT
A simple and convenient method of simultaneous determinations of effects of any set of chemical compounds on enzymatic hydrolysis of phospholipids by using the method of diffusion phospholipase A2 in a lecithin-agarose gel.
Subject(s)
Phospholipases A/analysis , Animals , Enzyme Activation , Humans , Hydrolysis , Phospholipases A/metabolism , Phospholipases A2 , Phospholipids/metabolismABSTRACT
Effect of ascorbate-dependent lipid peroxidation on activity of Mg2+-ATPase was studied in rat brain and liver tissues. Lipid peroxidation was shown to inactivate Mg2+-ATPase in the fraction of "heavy" brain microsomes. The rate of inactivation was directly related to the amount of the primary products of lipid peroxidation, accumulating in membrane lipids. At the same time, more intensive lipid peroxidation, as evidenced by content of diene conjugates and malonic dialdehyde, did not affect the liver Mg2+-ATPase.