Thioesterification of 2-arylpropionic acids by recombinant acyl-coenzyme Asynthetases (ACS1 and ACS2)

2-Arylpropionic acids are a class of frequently used nonsteroidal anti-infl ammatory drugs exhibiting a potent inhibition of cyclooxygenase isoforms su pported by the (+)S-enantiomer alone. Nevertheless, some of these compounds in the (-)R configuration may undergo extensive inversion of configuration to their antipode. The key molecular basis for this mechanism invokes the stereoselective formation of the coenzyme A (CoA) thioester of the 2-arylpr opionic acid by long-chain acyl-CoA synthetases (ACSs). In this report, rat recombinant ACS1 and ACS2 enzymes, constitutively highly expressed in adul t rat liver and brain, respectively, have been overproduced in Escherichia coli strains and purified to homogeneity to investigate the involvement of these enzymes in the thioesterification of fenoprofen and ibuprofen. Recomb inant ACS1 efficiently catalyzed both nonsteroidal anti-inflammatory drugs with Michaelis-Menten parameters of K-M = 1686 +/- 93 mu M, V-max = 353 +/- 45 nmol/min/mg protein for (-)R-ibuprofen and K-M = 103 +/- 12 mu M, V-max = 267 +/- 10 nmol/min/mg protein for (-)R-fenoprofen, and exhibited a mark ed stereoselectivity in favor of the (-)R-enantiomer. Recombinant ACS2, a c losely related sequence with ACS1, exhibited a lower enzymatic efficacy fro m 7- to 130-fold for (-)R-ibuprofen and (-)R-fenoprofen, respectively. On t he basis of these findings and considering the level of tissue expression o f the different long-chain ACSs, ACS1 appears to be the major enzyme involv ed in the first step of the chiral inversion of 2-arylpropionic acids. Neve rtheless, the participation of other ACS isoforms of minor quantitative imp ortance could not be excluded in the thioesterification of xenobiotics.