Inhibitors of CoA-independent transacylase block the movement of arachidonate into 1-ether-linked phospholipids of human neutrophils.
The enzyme CoA-independent transacylase (CoA-IT) has been proposed to mediate the movement of arachidonate between phospholipid subclasses and influence the formation of arachidonic acid metabolites and platelet-activating factor. To substantiate the critical role of CoA-IT, we have developed two structurally diverse inhibitors of CoA-IT activity, SK&F 98625 [diethyl 7-(3,4,5-triphenyl-2-oxo-2,3-dihydro-imidazole-1-yl)heptane phosphonate] and SK&F 45905 [2-[2-(3-4-chloro-3-(trifluoromethyl)phenyl)-ureido]-4- (trifluoromethyl)phenoxy]-4,5-dichlorobenzenesulfonic acid]. These compounds were tested for their capacity to block microsomal CoA-IT activity using two assay systems, the transacylation of 1-alkyl-2-lyso-sn-glycero-3-phosphocholine (GPC) and the transfer of [14C]arachidonate from 1-acyl-2-[14C]arachidonoyl-GPC to lyso-PE. Both SK&F 98625 and SK&F 45905 inhibited CoA-IT activity (IC50s 6-19 microM) in these two assays. In contrast, SK&F 98625 or SK&F 45905 had little or no effect on other lipid-modifying activities, including CoA-dependent acyltransferase or acetyltransferase. Kinetic analysis revealed that both SK&F 98625 and SK&F 45905 interact directly with the enzyme and prevented the acylation of lysophospholipids in a competitive manner. In intact human neutrophils, both SK&F 98625 and SK&F 45905 completely blocked the movement of [3H]arachidonate from 1-acyl-linked phospholipids into 1-alkyl-2-arachidonoyl-GPC and 1-alk-1'-enyl-2-arachidonoyl-GPE. In contrast, these compounds did not inhibit the incorporation of free arachidonic acid into cellular lipids indicating that they did not alter CoA-dependent acyl transferase activities in the intact cell.(ABSTRACT TRUNCATED AT 250 WORDS)
Chilton
F H
FH
Section on Pulmonary and Critical Care Medicine, Bowman Gray School of Medicine, Winston-Salem, North Carolina 27157-1054, USA.
Fonteh
A N
AN
Sung
C M
CM
Hickey
D M
DM
Torphy
T J
TJ
Mayer
R J
RJ
Marshall
L A
LA
Heravi
J D
JD
Winkler
J D
JD
D000217:Acyltransferases / Q000037:antagonists & inhibitors / Q000097:blood*; D016718:Arachidonic Acid / Q000097:blood*; D001557:Benzenesulfonates / Q000494:pharmacology*; D002460:Cell Line; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D007700:Kinetics; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology; D009504:Neutrophils / Q000201:enzymology*; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D010742:Phospholipid Ethers / Q000097:blood*; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014508:Urea / Q000031:analogs & derivatives* / Q000494:pharmacology
C093344:2-(2-(3-(4-chloro-3-(trifluoromethyl)phenyl)ureido)-4-(trifluoromethyl)phenoxy)-4,5-dichlorobenzenesulfonic acid; D001557:Benzenesulfonates; D007093:Imidazoles; D009943:Organophosphorus Compounds; D010742:Phospholipid Ethers; C093303:SK&F 98625; D016718:Arachidonic Acid; D014508:Urea; D000217:Acyltransferases; C039766:arachidonyl transacylase