title: Inhibition of phospholipase A1, lipase and galactolipase activities of pancreatic lipase-related protein 2 by methyl arachidonyl fluorophosphonate (MAFP).
abstract: Methyl arachidonyl fluorophosphonate (MAFP) is a known inhibitor of cytosolic phospholipase A2 and some other serine enzymes. MAFP was found here to be an irreversible inhibitor of human pancreatic lipase-related protein 2 (HPLRP2), an enzyme displaying lipase, phospholipase A1 and galactolipase activities. In the presence of MAFP, mass spectrometry analysis of HPLRP2 revealed a mass increase of 351Da, suggesting a covalent binding of MAFP to the active site serine residue. When HPLRP2 was pre-incubated with MAFP before measuring residual activity, a direct inhibition of HPLRP2 occurred, confirming that HPLRP2 has an active site freely accessible to solvent and differs from most lipases in solution. HPLRP2 activities on tributyrin (TC4), phosphatidylcholine (PC) and monogalactosyl dioctanoylglycerol (C8-MGDG) were equally inhibited under these conditions. Bile salts were not required to trigger the inhibition, but they significantly increased the rate of HPLRP2 inhibition, probably because of MAFP micellar solubilization. Since HPLRP2 is active on various substrates that self-organize differently in the presence of water, HPLRP2 inhibition by MAFP was tested in the presence of these substrates after adding MAFP in the course of the lipolysis reaction. In this case, the rates of inhibition of lipase, phospholipase A1 and galactolipase activities were not equivalent (triglycerides>PC>MGDG), suggesting different enzyme/inhibitor partitioning between the aqueous phase and lipid aggregates. The inhibition by MAFP of a well identified phospholipase A1 (HPLRP2), present in pancreatic juice and also in human monocytes, indicates that MAFP cannot be used for discriminating phospholipase A2 from A1 activities at the cellular level.
authors: CNRS-Aix-Marseille Université-Enzymologie Interfaciale et Physiologie de la Lipolyse-UMR 7282, 31 chemin Joseph Aiguier, 13402 Marseille cedex 20, France.
authors: Sawsan
authors: S
authors: Amara
authors: Vincent
authors: V
authors: Delorme
authors: Michel
authors: M
authors: Record
authors: Frédéric
authors: F
authors: Carrière
mesh_terms: D001095:Arachidonic Acids / Q000494:pharmacology*; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D008049:Lipase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008066:Lipolysis; D063065:Organophosphonates / Q000494:pharmacology*; D054466:Phospholipases A1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D001095:Arachidonic Acids; D004791:Enzyme Inhibitors; D063065:Organophosphonates; C104810:methyl arachidonylfluorophosphonate; D002265:Carboxylic Ester Hydrolases; C019262:galactolipase; D008049:Lipase; C075988:pancreatic lipase related protein 2; D054466:Phospholipases A1