Grant D M, Blum M, Beer M, Meyer U A
Department of Pharmacology, University of Basel, Switzerland.
Mol Pharmacol. 1991 Feb;39(2):184-91.
A genetic polymorphism of human liver arylamine N-acetyltransferase (NAT; EC 2.3.1.5) enzyme activity divides populations into distinguishable "slow acetylator" and "rapid acetylator" phenotypes. Two human genes, NAT1 and NAT2, encoding NAT proteins [DNA Cell Biol. 9:193-203 (1990)] were transiently expressed in cultured monkey kidney COS-1 cells, and the resulting recombinant NAT1 and NAT2 proteins were compared with N-acetyltransferase activities in human liver cytosol with respect to their stability, chromatographic behavior on anion exchange columns, electrophoretic mobility, and arylamine acceptor substrate specificity. NAT1 was far less stable in vitro than NAT2. Under conditions designed to optimize enzyme stability, anion exchange chromatography experiments revealed that enzymes corresponding to both recombinant NAT1 and NAT2 were expressed in human liver. Recombinant and human liver NAT1 enzymes showed the same characteristic selectivity (low apparent Km, high Vmax) for the "monomorphic" substrates p-aminosalicylic acid and p-aminobenzoic acid. Such substrates fail to discriminate between the acetylator phenotypes in vivo. The same criteria established that recombinant NAT2 was indistinguishable from one of two previously observed N-acetyltransferases (NAT2A and NAT2B) whose liver contents correlate with acetylator phenotype in human populations. Recombinant NAT2 and the liver NAT2 isoforms NAT2A and NAT2B selectivity N-acetylated the "polymorphic" substrates sulfamethazine and procainamide, whose disposition in vivo is affected by the acetylation polymorphism. Interestingly, the carcinogen 2-aminofluorene was very efficiently metabolized by both NAT1 and NAT2. Independent regulation of NAT1 and NAT2 genes was suggested by a lack of correlation of NAT1 and NAT2 enzyme activities in cytosols from 39 human livers. The results provide strong evidence that the NAT2 locus is the site of the human acetylation polymorphism. In addition, the use of recombinant NAT1 and NAT2 will allow us to predict whether any given arylamine will be polymorphically acetylated in humans.
人类肝脏芳胺N - 乙酰基转移酶（NAT；EC 2.3.1.5）的基因多态性使人群分为可区分的“慢乙酰化者”和“快乙酰化者”表型。编码NAT蛋白的两个人类基因NAT1和NAT2[《DNA与细胞生物学》9:193 - 203(1990)]在培养的猴肾COS - 1细胞中瞬时表达，然后将产生的重组NAT1和NAT2蛋白与人类肝脏胞质溶胶中的N - 乙酰基转移酶活性在稳定性、阴离子交换柱上的色谱行为、电泳迁移率和芳胺受体底物特异性方面进行比较。NAT1在体外比NAT2稳定性差得多。在旨在优化酶稳定性的条件下，阴离子交换色谱实验表明，重组NAT1和NAT2对应的酶在人类肝脏中均有表达。重组和人类肝脏NAT1酶对“单态性”底物对氨基水杨酸和对氨基苯甲酸表现出相同的特征选择性（低表观Km，高Vmax）。这类底物在体内无法区分乙酰化者表型。同样的标准确定重组NAT2与先前观察到的两种N - 乙酰基转移酶（NAT2A和NAT2B）之一无法区分，其肝脏含量与人类群体中的乙酰化者表型相关。重组NAT2以及肝脏NAT2同工型NAT2A和NAT2B对“多态性”底物磺胺二甲嘧啶和普鲁卡因酰胺具有选择性N - 乙酰化作用，它们在体内的处置受乙酰化多态性影响。有趣的是，致癌物2 - 氨基芴被NAT1和NAT2都非常有效地代谢。39个人类肝脏胞质溶胶中NAT1和NAT2酶活性缺乏相关性，提示NAT1和NAT2基因存在独立调控。这些结果提供了强有力的证据，表明NAT2基因座是人类乙酰化多态性的位点。此外，重组NAT1和NAT2的应用将使我们能够预测任何给定的芳胺在人类中是否会发生多态性乙酰化。
