Centers of Excellence in Environmental Toxicology and Cancer Pharmacology, Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6084, USA.
J Biol Chem. 2012 Aug 24;287(35):29909-20. doi: 10.1074/jbc.M112.386052. Epub 2012 Jul 9.
Polycyclic aromatic hydrocarbons (PAH) are environmental and tobacco carcinogens. Human aldo-keto reductases catalyze the metabolic activation of proximate carcinogenic PAH trans-dihydrodiols to yield electrophilic and redox-active o-quinones. Benzo[a]pyrene-7,8-dione a representative PAH o-quinone is reduced back to the corresponding catechol to generate a futile redox-cycle. We investigated whether sulfonation of PAH catechols by human sulfotransferases (SULT) could intercept the catechol in human lung cells. RT-PCR identified SULT1A1, -1A3, and -1E1 as the isozymes expressed in four human lung cell lines. The corresponding recombinant SULTs were examined for their substrate specificity. Benzo[a]pyrene-7,8-dione was reduced to benzo[a]pyrene-7,8-catechol by dithiothreitol under anaerobic conditions and then further sulfonated by the SULTs in the presence of 3'-[(35)S]phosphoadenosine 5'-phosphosulfate as the sulfonate group donor. The human SULTs catalyzed the sulfonation of benzo[a]pyrene-7,8-catechol and generated two isomeric benzo[a]pyrene-7,8-catechol O-monosulfate products that were identified by reversed phase HPLC and by LC-MS/MS. The various SULT isoforms produced the two isomers in different proportions. Two-dimensional (1)H and (13)C NMR assigned the two regioisomers of benzo[a]pyrene-7,8-catechol monosulfate as 8-hydroxy-benzo[a]pyrene-7-O-sulfate (M1) and 7-hydroxy-benzo[a]pyrene-8-O-sulfate (M2), respectively. The kinetic profiles of three SULTs were different. SULT1A1 gave the highest catalytic efficiency (k(cat)/K(m)) and yielded a single isomeric product corresponding to M1. By contrast, SULT1E1 showed distinct substrate inhibition and formed both M1 and M2. Based on expression levels, catalytic efficiency, and the fact that the lung cells only produce M1, it is concluded that the major isoform that can intercept benzo[a]pyrene-7,8-catechol is SULT1A1.
多环芳烃（PAH）是环境和烟草致癌物质。人类醛酮还原酶催化代谢激活近致癌性 PAH 反式二氢二醇生成亲电和氧化还原活性的邻醌。苯并[a]芘-7,8-二酮是一种代表性的 PAH 邻醌，被还原回相应的儿茶酚以生成无效的氧化还原循环。我们研究了人类磺基转移酶（SULT）对 PAH 儿茶酚的磺化是否可以拦截人肺细胞中的儿茶酚。RT-PCR 鉴定出 SULT1A1、-1A3 和-1E1 是四种人肺细胞系中表达的同工酶。相应的重组 SULT 被检测其底物特异性。在无氧条件下，二硫苏糖醇还原苯并[a]芘-7,8-二酮为苯并[a]芘-7,8-儿茶酚，然后在 3'-[(35)S]磷酸腺苷 5'-磷酸硫酸作为磺酸盐供体的存在下，由 SULT 进一步磺化。人 SULT 催化苯并[a]芘-7,8-儿茶酚的磺化，并生成两种异构的苯并[a]芘-7,8-儿茶酚 O-单硫酸盐产物，通过反相 HPLC 和 LC-MS/MS 鉴定。各种 SULT 同工酶以不同的比例产生这两种异构体。二维（1)H 和（13)C NMR 将苯并[a]芘-7,8-儿茶酚单硫酸盐的两种区域异构体分配为 8-羟基-苯并[a]芘-7-O-硫酸盐（M1）和 7-羟基-苯并[a]芘-8-O-硫酸盐（M2）。三种 SULT 的动力学曲线不同。SULT1A1 给出了最高的催化效率（k(cat)/K(m)），并产生了与 M1 对应的单一异构产物。相比之下，SULT1E1 表现出明显的底物抑制作用，并形成了 M1 和 M2。基于表达水平、催化效率以及肺细胞仅产生 M1 的事实，可以得出结论，能够拦截苯并[a]芘-7,8-儿茶酚的主要同工酶是 SULT1A1。
