Metabolic inversion of (R)-ibuprofen. Epimerization and hydrolysis of ibuprofenyl-coenzyme A.
Ibuprofen [(racemic)2-(4-isobutylphenyl)propionic acid] has been proposed but not directly demonstrated to undergo unidirectional inversion from the (R)- to the (S)-configuration via a coenzyme A (CoA) thioester intermediate. Chemically synthesized (R)- and (S)-ibuprofenyl-CoA, and rat and human liver homogenates were used to investigate the relative rates of ibuprofenyl-CoA epimerization and hydrolysis. Rat whole liver homogenate completely epimerized (R)- or (S)-ibuprofenyl-CoA, whereas hydrolysis of this intermediate occurred at a much slower rate. Rat liver mitochondria was the most efficient at both epimerizing and hydrolyzing ibuprofenyl-CoA, whereas rat liver microsomes hydrolyzed ibuprofenyl-CoA at a rate similar to whole liver homogenate but had very little epimerization activity. Rat liver cytosol was the poorest at hydrolyzing ibuprofenyl-CoA but had substantial epimerization capability. Whole liver homogenate from human tissue was less efficient at epimerizing but as efficient at hydrolyzing ibuprofenyl-CoA as rat whole liver homogenate. No stereoselectivity of either epimerization or hydrolysis was noted for any of the enzyme preparations studied. This study demonstrates that the inversion of (R)-ibuprofen occurs, at least in part, via the epimerization of the metabolic intermediate, ibuprofenyl-CoA, in both rat and human liver tissues.
Department of Medicine, Indiana University School of Medicine, Wishard Memorial Hospital, Indianapolis 46202-2879.
T S
TS
Tracy
S D
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Hall
D000818:Animals; D003600:Cytosol / Q000201:enzymology; D006801:Humans; D006868:Hydrolysis; D007052:Ibuprofen / Q000737:chemistry / Q000378:metabolism*; D008099:Liver / Q000166:cytology; D008862:Microsomes, Liver / Q000201:enzymology*; D019998:Racemases and Epimerases / Q000378:metabolism; D051381:Rats; D013237:Stereoisomerism
D019998:Racemases and Epimerases; D007052:Ibuprofen