In vitro fenoprofenyl–coenzyme a thioester formation: Interspecies variations

In vitro coenzyme A thioester formation from (−)‐(R)‐fenoprofen (FPF) and palmitic acid has been studied using liver microsomes from rat, guinea pig, sheep, and dog. In every species with both palmitic acid or (−)‐(R)‐fenoprofen, the Lineweaver–Burk plot was linear in the substrate concentration range used and as a consequence agrees with the involvement of only one isoenzyme (or different isoenzymes of similar K m values). The V max values for the thioesterification of (−)‐(R)‐fenoprofen present large species variations from 2.1 ± 1.0 with sheep liver microsomes to 60.6 ± 11 nmol/min/mg with dog liver microsomes. These values statistically significantly correlate ( r = 0.94) to the V max values observed when palmitic acid was used as a substrate. Furthermore palmitic acid inhibited (−)‐(R)‐fenoprofen–CoA formation in the same extent in all animal species. The stereoselectivity of the thioesterification was also species dependent. © 1995 Wiley‐Liss, Inc.