2-Arylpropionyl-CoA epimerase: partial peptide sequences and tissue localization.

The R-enantiomers of 2-arylpropionic acids (2-APAs) such as ibuprofen (IBU) exhibit the phenomenon of species- and substrate-dependent metabolic chiral inversion. Only R-enantiomers are activated to acyl-CoA-thioesters by an acyl-CoA-synthetase via an adenylate intermediate. The acyl-CoA-thioesters are substrates for an epimerase, which is responsible for chiral inversion. A 42 kDa epimerase from the cytosolic fraction of rat livers was isolated and purified to homogeneity. Polyclonal antibodies were raised against the epimerase in rabbits. The anti-epimerase antibodies were used for affinity column chromatography to separate homogeneous protein for amino acid sequence analysis. Sequence data analysis of 3 internal peptide sequences showed 50% and more homology with regions of enzymes involved in fatty acid metabolism. The polyclonal anti-epimerase antibodies were used to analyze the tissue distribution of the in guinea pigs and rats by Western blot analysis. Furthermore, the correlation of inversion enzyme activity in various tissues under comparable incubation conditions and cross-reactivity in Western blot analysis was investigated.