Substrate level modulation of the activity of phospholipase A2 in vitro by 12-O-tetradecanoylphorbol-13-acetate.
The action of porcine pancreatic phospholipase A2 towards fluorescent phospholipid analogs is either enhanced or suppressed by 4 beta-12-O-tetradecanoylphorbol-13- acetate (TPA), depending on the chemical structure of the substrate and the concentration of Ca2+. In the presence of nmolar Ca2+ concentrations increasing [TPA] enhanced by approx. 5-fold the rate of hydrolysis of the pyrene-labelled acidic alkyl-acyl phospholipid, 1-octacosanyl-2-[6- (pyrene-1-yl)] hexanoyl-sn-glycero-3-phosphatidylmethanol. Maximal effect was obtained at high TPA/substrate molar ratios approaching 1:2. In the presence of 4 mM CaCl2 maximal activation was reduced to approximately 1.5-fold. With the corresponding phosphatidylcholine derivative as a substrate increasing [TPA] reduced fatty acid release maximally by 90% both at low [Ca2+] as well as in the presence of 4 mM CaCl2. Essentially identical results were obtained using 4 alpha-TPA, a stereoisomer which does not activate protein kinase C.
Mustonen
P
P
Department of Medical Chemistry, University of Helsinki, Finland.
Kinnunen
P K
PK
D000818:Animals; D016477:Artifacts; D002118:Calcium / Q000494:pharmacology; D004789:Enzyme Activation; D005456:Fluorescent Dyes / Q000378:metabolism; D006868:Hydrolysis; D010179:Pancreas / Q000201:enzymology; D010741:Phospholipases A / Q000187:drug effects / Q000378:metabolism*; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism*; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D005456:Fluorescent Dyes; D010743:Phospholipids; D010741:Phospholipases A; D054467:Phospholipases A2; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium