Yerokun T, Kirlin W G, Trinidad A, Ferguson R J, Ogolla F, Andrews A F, Brady P K, Hein D W
Department of Pharmacology, Morehouse School of Medicine, Atlanta, GA 30310-1495.
Drug Metab Dispos. 1989 May-Jun;17(3):231-7.
Recent studies from our laboratory have shown relatively high levels of polymorphic N-acetyltransferase (NAT)(EC 2.3.1.5) activity toward carcinogenic arylamines in urinary bladder cytosol of humans and in the inbred hamster model of the N-acetylation polymorphism. The expression of this polymorphism is of interest because of the higher incidence of bladder cancer among human slow acetylators with documented exposures to arylamine bladder carcinogens. In this study, arylamine NAT activity was partially purified and characterized in inbred hamster urinary bladder cytosols of defined acetylator genotype. Acetylator gene-dose response relationships were observed for the N-acetylation of p-aminobenzoic acid, p-aminosalicyclic acid, and the arylamine carcinogens 2-aminofluorene, 4-aminobiphenyl, and beta-naphthylamine in hamster bladder cytosol. Partial purification of hamster bladder cytosol by anion-exchange fast protein liquid chromatography yielded two NAT isozymes that catalyzed the N-acetylation of each of the arylamine substrates. The catalytic activity of the first isozyme was acetylator genotype-dependent (polymorphic), whereas the second isozyme appeared to be acetylator genotype-independent (monomorphic). Catalytic activities between homozygous rapid, heterozygous, and homozygous slow acetylator genotypes were compared with respect to both initial rates and apparent maximum velocities. Comparison of homozygous rapid and slow acetylator bladder cytosol showed that the apparent Vmax for 2-aminofluorene NAT activity was significantly higher in rapid than slow acetylators (6-fold in cytosol, 50-fold in the polymorphic NAT isozyme). These results suggest a key role for a polymorphic NAT isozyme, regulated by the acetylator genotype and expressed in urinary bladder cytosol, in the initiation of bladder cancer via arylamine carcinogens.
我们实验室最近的研究表明，在人类膀胱细胞溶质以及N - 乙酰化多态性的近交仓鼠模型中，多态性N - 乙酰转移酶（NAT）（EC 2.3.1.5）对致癌芳胺具有相对较高的活性。这种多态性的表达备受关注，因为在有记录接触芳胺膀胱致癌物的人类慢乙酰化者中膀胱癌发病率较高。在本研究中，对特定乙酰化基因型的近交仓鼠膀胱细胞溶质中的芳胺NAT活性进行了部分纯化和表征。在仓鼠膀胱细胞溶质中，观察到对氨基苯甲酸、对氨基水杨酸以及芳胺致癌物2 - 氨基芴、4 - 氨基联苯和β - 萘胺的N - 乙酰化存在乙酰化基因剂量反应关系。通过阴离子交换快速蛋白质液相色谱对仓鼠膀胱细胞溶质进行部分纯化，得到了两种催化每种芳胺底物N - 乙酰化的NAT同工酶。第一种同工酶的催化活性依赖于乙酰化基因型（多态性），而第二种同工酶似乎与乙酰化基因型无关（单态性）。就初始速率和表观最大速度而言，比较了纯合快速、杂合和纯合慢乙酰化基因型之间的催化活性。纯合快速和慢乙酰化者膀胱细胞溶质的比较表明，2 - 氨基芴NAT活性的表观Vmax在快速乙酰化者中显著高于慢乙酰化者（细胞溶质中为6倍，多态性NAT同工酶中为50倍）。这些结果表明，一种由乙酰化基因型调控并在膀胱细胞溶质中表达的多态性NAT同工酶，在通过芳胺致癌物引发膀胱癌过程中起关键作用。
