The Nonenzymatic Reactivity of the Acyl-Linked Metabolites of Mefenamic Acid toward Amino and Thiol Functional Group Bionucleophiles
作者:Howard Horng、Leslie Z. Benet
DOI:10.1124/dmd.113.053223
日期:2013.11
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 μ M) 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 μ M) 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.
甲灭酸 (MFA) 是一种含羧酸的非甾体抗炎药物,在代谢过程中会生成具有化学反应的 MFA-1- O -酰基葡萄糖醛酸苷 (MFA-1- O -G)、MFA-酰基腺苷酸 (MFA-AMP) 和 MFA- S -酰基辅酶 A (MFA-CoA),它们都具有亲电性,能够酰化生物大分子上的亲核位点。在本研究中,我们研究了每种 MFA 乙酰连接代谢物在受体生物大分子 Gly、Tau、l-谷胱甘肽(GSH)和 N-乙酰半胱氨酸(NAC)上酰化氨基和硫醇官能团的非酶能力。在生理条件下,在缓冲液中将每种 MFA 乙酰连接代谢物(1 μ M)与 Gly、Tau、GSH 或 NAC(10 mM)进行体外培养,结果表明 MFA-CoA 对 GSH 和 NAC 的半胱氨酸-巯基酰化的反应活性分别是 MFA-AMP 的 11.5 倍和 19.5 倍。然而,MFA-AMP 对甘氨酸和 Tau 的反应活性更高,对牛磺酸 N-酰基酰胺化的反应活性是其相应 CoA 硫代酯的 17.5 倍,而 MFA-CoA 对甘氨酸的反应活性很小。此外,甲灭酸-S-酰基谷胱甘肽(MFA-GSH)对 NAC 的反应活性分别是 MFA-CoA 和 MFA-AMP 的 5.6 倍和 108 倍。与 MFA-AMP 和 MFA-CoA 相比,MFA-1- O -G 对所有四种亲核物的反应性都不明显。在大鼠体外肝细胞 MFA(100 μ M)培养液中也检测到了 MFA-AMP、MFA-CoA、MFA-1- O -G、MFA-GSH 和甲灭酸-牛磺酸,而甲灭酸-甘氨酸没有检测到。这些结果表明,MFA-AMP 会选择性地与甘氨酸和赖氨酸的氨基官能团发生非酶反应,MFA-CoA 会选择性地与 GSH 和 NAC 的硫醇官能团发生非酶反应,而 MFA-GSH 会与 GSH 的硫醇官能团发生非酶反应,所有这些反应都有可能在体内引发特异性毒性。