Metabolic inversion of (R)-ibuprofen. Formation of ibuprofenyl-coenzyme A.
Ibuprofen [(racemic)2-(4-isobutylphenyl)propionic acid] undergoes metabolic inversion via formation, epimerization, and hydrolysis of the coenzyme A (CoA) thioester, ibuprofenyl-CoA. In this study, (R)-ibuprofen was incubated with either rat whole liver homogenate, human whole liver homogenate, rat liver mitochondria, or rat liver microsomes, and the formation of ibuprofenyl-CoA measured. Rat whole liver homogenate (Vmax/KM = 0.022 +/- 0.005 ml/min/mg protein) was approximately 4-fold more efficient at forming ibuprofenyl-CoA than human whole liver homogenate (Vmax/KM, = 0.005 +/- 0.004 ml/min/mg protein). Rat liver microsomes (Vmax/KM = 0.047 +/- 0.019 ml/min/mg protein) were approximately 2-fold more efficient than rat whole liver homogenate at forming ibuprofenyl-CoA, whereas rat liver mitochondria (Vmax/KM = 0.027 +/- 0.017 ml/min/mg protein) did not differ from whole liver homogenate. Palmitic (Ki = 0.005 mM) and octanoic acids (Ki = 0.19 mM) were capable of inhibiting ibuprofenyl-CoA formation, whereas propionic acid had no effect, suggesting the possible involvement of both long- and medium-chain fatty acyl-CoA synthetases. Of the xenobiotics tested, only bezafibrate (Ki = 0.85 mM) and (S)-ibuprofen (Ki = 0.095 mM in rats, 0.32 mM in human tissue) were capable of substantially inhibiting ibuprofenyl-CoA formation. Thus, it appears that the metabolic inversion of ibuprofen involves lipid-metabolizing pathways and may be affected by fatty acids or xenobiotics.
Tracy
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TS
Department of Medicine, Indiana University School of Medicine, Wishard Memorial Hospital.
Wirthwein
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DP
Hall
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SD
D000818:Animals; D003065:Coenzyme A / Q000378:metabolism*; D003066:Coenzyme A Ligases / Q000378:metabolism; D006801:Humans; D007052:Ibuprofen / Q000378:metabolism*; D007700:Kinetics; D008862:Microsomes, Liver / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013045:Species Specificity; D013237:Stereoisomerism; D013347:Subcellular Fractions / Q000378:metabolism; D014635:Valproic Acid / Q000494:pharmacology; D015262:Xenobiotics / Q000494:pharmacology
D015262:Xenobiotics; D014635:Valproic Acid; D003066:Coenzyme A Ligases; D003065:Coenzyme A; D007052:Ibuprofen