Ware J A, Svensson C K
Department of Pharmaceutical Sciences, Wayne State University, Detroit, MI 48202, USA.
Biochem Pharmacol. 1996 Nov 22;52(10):1613-20. doi: 10.1016/s0006-2952(96)00567-9.
Experimental and clinical evidence indicates that AcCoA:arylamine N-acetyltransferases (NATs; EC 2.3.1.5) are involved in the bioactivation and inactivation of a wide variety of arylamine, hydrazine, and carcinogenic arylamine xenobiotics. Longitudinal distribution of NATs in the intestine of the hamster, mouse, and two strains of rat was examined utilizing the model arylamine substrates procainamide(PA) and p-aminobenzoic acid (PABA) for the monomorphic (NAT1) and polymorphic (NAT2) enzymes in the rodent. NAT1 and NAT2 were distributed quite differently in each species examined. In particular, rat intestinal NATs were distributed equally throughout the intestinal tract. In contrast, hamster intestinal NATs decreased in activity from the proximal small intestine to the distal large intestine. Mouse NAT2 activity was highest in the cecum, whereas NAT1 was highest in the proximal small intestine. Although these model substrates have been shown to be selective for NATs, they are not specific. Therefore, a series of biochemical studies were undertaken to evaluate NAT multiplicity in the intestine of the F-344 rat. To assess multiplicity of NAT expression, selective inhibition, differential sensitivity to heat inactivation, and kinetic analysis were performed on intestinal cytosol. Eadie-Hofstee transformation of PA N-acetylation yielded a curvilinear plot indicative that a low affinity-high capacity enzyme aside from NAT1 (presumably NAT2) was contributing to PA N-acetylation activity. PA activity was found to exhibit approximately 4- to 5-fold greater thermostability than PABA activity. Furthermore, PA acetylation could be inhibited selectively with vinyl fluorenyl ketone (2.5 to 5 microM) but not with methotrexate (up to 2 mM). Taken together, these studies suggest the expression of both NAT1 and NAT2 in the intestine of the F-344 rat.
实验和临床证据表明，乙酰辅酶A：芳胺N - 乙酰基转移酶（NATs；EC 2.3.1.5）参与多种芳胺、肼和致癌性芳胺类外源性物质的生物活化和失活过程。利用模型芳胺底物普鲁卡因酰胺（PA）和对氨基苯甲酸（PABA），对仓鼠、小鼠和两种大鼠品系肠道中NATs的纵向分布进行了检测，以研究啮齿动物中单一型（NAT1）和多态型（NAT2）酶的情况。在每个被检测的物种中，NAT1和NAT2的分布差异很大。特别是，大鼠肠道中的NATs在整个肠道中分布均匀。相比之下，仓鼠肠道中的NATs活性从近端小肠到远端大肠逐渐降低。小鼠的NAT2活性在盲肠中最高，而NAT1在近端小肠中最高。尽管这些模型底物已被证明对NATs具有选择性，但并非特异性。因此，开展了一系列生化研究以评估F - 344大鼠肠道中NAT的多样性。为了评估NAT表达的多样性，对肠道胞质溶胶进行了选择性抑制、对热失活的差异敏感性以及动力学分析。PA N - 乙酰化的Eadie - Hofstee转换产生了一条曲线，表明除了NAT1（可能是NAT2）之外，一种低亲和力 - 高容量的酶也参与了PA N - 乙酰化活性。发现PA活性的热稳定性比PABA活性高约4至5倍。此外，PA乙酰化可被乙烯基芴基酮（2.5至5 microM）选择性抑制，但不能被甲氨蝶呤（高达2 mM）抑制。综上所述，这些研究表明F - 344大鼠肠道中同时表达NAT1和NAT2。
