Trifluoromethyl ketones and methyl fluorophosphonates as inhibitors of group IV and VI phospholipases A2: structure-function studies with vesicle, micelle, and membrane assays1This paper is dedicated to the memory of Prof. H.M. Verheij.1

Abstract

A series of fatty alkyl trifluoromethyl ketones and methyl fluorophosphonates have been prepared and tested as inhibitors and inactivators of human groups IV and VI phospholipases A(2) (cPLA(2) and iPLA(2)). Compounds were analyzed with phospholipid vesicle-, detergent-phospholipid mixed-micelle-, and natural membrane-based assays, and, with few exceptions, the relative inhibitor potencies measured with the three assays were similar. Ph(CH(2))(4)COCF(3) and Ph(CH(2))(4)PO(OMe)F emerged as a potent inhibitor and inactivator, respectively, of iPLA(2), and both are poorly effective against cPLA(2). Of all 13 fatty alkyl trifluoromethyl ketones tested, the trifluoromethyl ketone analog of arachidonic acid is the most potent cPLA(2) inhibitor, and structurally similar compounds including the trifluoromethyl ketone analog of docosahexenoic acid are much poorer cPLA(2) inhibitors. Inactivation of cPLA(2) by fatty alkyl fluoromethylphosphonates is greatly promoted by binding of enzyme to the interface. The use of both vesicles and mixed micelles to assay phospholipase A(2) inhibitors and inactivators present at low mol fraction in the interface provides reliable rank order potencies of a series of compounds that correlate with their behavior in a natural membrane assay.

Arachidonyl trifluoromethyl ketone ameliorates experimental autoimmune encephalomyelitis via blocking peroxynitrite formation in mouse spinal cord white matter

“…It is known that AACOCF3 not only inhibits cPLA 2 , but also inhibits iPLA 2 and COX-2 (Ghomashchi et al, 1999;Kalyvas and David, 2004). Recently, it has been shown that the inhibitors of cPLA 2 , iPLA 2 and sPLA 2 can all reduce the severity of EAE, and activation of different PLA 2 isoforms may be involved in the different stages of the disease (Kalyvas et al, 2009).…”

Inhibition of Platelet-Activating Factor (PAF) Acetylhydrolase by Methyl Arachidonyl Fluorophosphonate Potentiates PAF Synthesis in Thrombin-Stimulated Human Coronary Artery Endothelial Cells

“…The compound competes with endogenous phospholipid molecules for the active catalytic site on the PLA 2 enzyme. MAFP has been shown to irreversibly inhibit soluble cytosolic cPLA 2 and iPLA 2 , possibly by phosphorylation of the active site serine residue (Ghomashchi et al, 1999). Although the relatively polar MAFP has direct access to the catalytic site of soluble PLA 2 isoforms, the active site serine residue of membrane-associated iPLA 2 may be "protected" from this inhibitor.…”

Crystal structure of FAS thioesterase domain with polyunsaturated fatty acyl adduct and inhibition by dihomo-γ-linolenic acid

“…Long-chain polyunsaturated fatty acyl fluorophosphonates have been demonstrated previously to irreversibly inactivate phospholipases through rapid phosphorylation of a reactive serine residue in the active site (24,25). Our studies reported here were set in motion by the determination of the X-ray structure of the hFAS TE domain treated with twofold excess of methyl γ-linolenyl fluorophosphonate (MGLFP; Scheme S1) (see Methods and SI Methods).…”