title: The nonenzymatic reactivity of the acyl-linked metabolites of mefenamic acid toward amino and thiol functional group bionucleophiles.
abstract: Mefenamic acid (MFA), a carboxylic acid-containing nonsteroidal anti-inflammatory drug, is metabolized into the chemically-reactive MFA-1-O-acyl-glucuronide (MFA-1-O-G), MFA-acyl-adenylate (MFA-AMP), and the MFA-S-acyl-coenzyme A (MFA-CoA), all of which are electrophilic and capable of acylating nucleophilic sites on biomolecules. In this study, we investigate the nonenzymatic ability of each MFA acyl-linked metabolite to transacylate amino and thiol functional groups on the acceptor biomolecules Gly, Tau, l-glutathione (GSH), and N-acetylcysteine (NAC). In vitro incubations with each of the MFA acyl-linked metabolites (1 μM) in buffer under physiologic conditions with Gly, Tau, GSH, or NAC (10 mM) revealed that MFA-CoA was 11.5- and 19.5-fold more reactive than MFA-AMP toward the acylation of cysteine-sulfhydryl groups of GSH and NAC, respectively. However, MFA-AMP was more reactive toward both Gly and Tau, 17.5-fold more reactive toward the N-acyl-amidation of taurine than its corresponding CoA thioester, while MFA-CoA displayed little reactivity toward glycine. Additionally, mefenamic acid-S-acyl-glutathione (MFA-GSH) was 5.6- and 108-fold more reactive toward NAC than MFA-CoA and MFA-AMP, respectively. In comparison with MFA-AMP and MFA-CoA, MFA-1-O-G was not significantly reactive toward all four bionucleophiles. MFA-AMP, MFA-CoA, MFA-1-O-G, MFA-GSH, and mefenamic acid-taurine were also detected in rat in vitro hepatocyte MFA (100 μM) incubations, while mefenamic acid-glycine was not. These results demonstrate that MFA-AMP selectively reacts with the amino functional groups of glycine and lysine nonenzymatically, MFA-CoA selectively reacts nonenzymatically with the thiol functional groups of GSH and NAC, and MFA-GSH reacts with the thiol functional group of GSH nonenzymatically, all of which may potentially elicit an idiosyncratic toxicity in vivo.
authors: Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California.
authors: Howard
authors: H
authors: Horng
authors: Leslie Z
authors: LZ
authors: Benet
mesh_terms: D000111:Acetylcysteine / Q000378:metabolism; D000214:Acyl Coenzyme A / Q000378:metabolism; D000215:Acylation / Q000502:physiology; D000249:Adenosine Monophosphate / Q000378:metabolism; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000378:metabolism*; D005965:Glucuronates / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D008297:Male; D008528:Mefenamic Acid / Q000031:analogs & derivatives / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013438:Sulfhydryl Compounds / Q000378:metabolism*
chemical_list: D000214:Acyl Coenzyme A; D000894:Anti-Inflammatory Agents, Non-Steroidal; D005965:Glucuronates; D013438:Sulfhydryl Compounds; C084198:1-O-(2-(2,3-dimethylphenyl)aminobenzoyl)glucopyranuronic acid; D008528:Mefenamic Acid; D000249:Adenosine Monophosphate; D005978:Glutathione; D000111:Acetylcysteine
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