CYP2A13 expressed in human bladder metabolically activates 4-aminobiphenyl
CYP2A13 expressed in human bladder metabolically activates 4-aminobiphenyl
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DOI：
10.1002/ijc.22136
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发表时间：
2006-12-01
影响因子：
6.4
通讯作者：
Yokoi, Tsuyoshi
中科院分区：
文献类型：
--
作者：
Nakajima, Miki;Itoh, Masahiro;Yokoi, Tsuyoshi
吸烟是膀胱癌的主要危险因素。4-氨基联苯（ABP）等芳香胺是烟草烟雾中的主要致癌物。尽管普遍认为ABP在人肝脏中通过CYP 1A 2的N-羟基化代谢活化，但先前使用Cyp 1a 2缺失小鼠进行的研究表明其他酶也参与其中。Umu试验发现，CYP 2A 13可代谢激活ABP，表现出遗传毒性。在E.大肠杆菌的平均浓度分别为38.5 ± 0.6 μ M和7.8 ± 0.0 pmol/min/pmol/min。重组CYP 1A 2的Km和V-max值分别为9.9 +/- 0.9 μ M和39.6 +/- 0.9 pmol/min/pmol Cmax，显示固有清除率比CYP 2A 13高20倍。在人膀胱中，CYP 2A 13 mRNA以相对高的水平表达，而非CYP 1A 2。人膀胱微粒体显示ABP N-羟化酶活性（K-m = 34.9 +/- 4.7 μ M和V-max = 57.5 +/- 1.9 pmol/min/mg蛋白），尽管固有清除率比人肝微粒体低5倍（K-m = 33.2 +/- 2.0 μ M和V-max = 293.9 +/- 5.8 pmol/min/mg蛋白）。人膀胱微粒体中的活性显著受8-甲氧基补骨脂素抑制，但不受氟伏沙明、抗CYP 1A 2或抗CYP 2A 6抗体抑制。CYP 2S 1在人膀胱中表达，与CYP 2A具有相对较高的氨基酸同一性，未显示出可检测的ABP N-羟化酶活性。总之，尽管无法确定人膀胱微粒体中负责ABP N-羟基化的酶，但我们发现CYP 2A 13代谢活化ABP。(c)2006威利-利斯公司
Cigarette smoking is the predominant risk factor for bladder cancer. Aromatic amines such as 4-aminobiphenyl (ABP) is the major carcinogens found in tobacco smoke. Although it is generally accepted that ABP is metabolically activated via N-hydroxylation by CYP1A2 in human liver, previous studies using Cyp1a2-null mice indicated the involvement of other enzyme(s). Here we found that CYP2A13 can metabolically activate ABP to show genotoxicity by Umu assay. The K-m and V-max values for ABP N-hydroxylation by recombinant CYP2A13 in E. coli were 38.5 +/- 0.6 mu M and 7.8 +/- 0.0 pmol/min/pmol CYP, respectively. The K-m and V-max values by recombinant CYP1A2 were 9.9 +/- 0.9 mu M and 39.6 +/- 0.9 pmol/min/pmol CYP, respectively, showing 20-fold higher intrinsic clearance than CYP2A13. In human bladder, CYP2A13 mRNA, but not CYP1A2, is expressed at a relatively high level. Human bladder microsomes showed ABP N-hydroxylase activity (K-m = 34.9 +/- 4.7 mu M and V-max = 57.5 +/- 1.9 pmol/min/mg protein), although the intrinsic clearance was 5-fold lower than that in human liver microsomes (K-m = 33.2 +/- 2.0 mu M and V-max = 293.9 +/- 5.8 pmol/min/mg protein). The activity in human bladder microsomes was prominently inhibited by 8-methoxypsoralen, but not by fluvoxamine, anti-CYP1A2 or anti-CYP2A6 antibodies. CYP2S1, which is expressed in human bladder and has relatively high amino acid identities with CYP2As, did not show detectable ABP N-hydroxylase activity. In conclusion, although the enzyme responsible for ABP N-hydroxylation in human bladder microsomes could not be determined, we found that CYP2A13 metabolically activates ABP. (c) 2006 Wiley-Liss, Inc.