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 microM 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 microM 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 microM 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 microM 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.

译文

吸烟是膀胱癌的主要危险因素。芳香胺 (例如4-氨基联苯 (ABP)) 是烟草烟雾中发现的主要致癌物。尽管人们普遍认为ABP通过CYP1A2在人肝脏中通过N-羟基化代谢激活,但先前使用Cyp1a2-null小鼠的研究表明其他酶的参与。在这里,我们发现CYP2A13可以通过Umu测定代谢激活ABP以显示遗传毒性。重组CYP2A13在大肠杆菌中abpn-羟基化的K(m) 和V(max) 值分别为38.5 +/- 0.6 microM和7.8 +/- 0.0 pmol/min/pmol CYP。重组CYP1A2的K(m) 和V(max) 值分别为9.9 +/- 0.9 microM和39.6 +/- 0.9 pmol/min/pmol CYP,显示出比CYP2A13高20倍的固有清除率。在人膀胱中,CYP2A13 mRNA而不是CYP1A2以相对较高的水平表达。人膀胱微粒体显示ABP N-羟化酶活性 (K(m) = 34.9 +/- 4.7微米和V(max) = 57.5 +/- 1.9 pmol/min/mg蛋白),虽然内在清除率比人肝微粒体低5倍 (K(m) = 33.2 +/- 2.0微米和V(max) = 293.9 +/- 5.8 pmol/min/mg蛋白)。8-甲氧基补骨脂素显着抑制人膀胱微粒体的活性,但氟伏沙明,anti-CYP1A2或anti-CYP2A6抗体不抑制人膀胱微粒体的活性。CYP2S1在人膀胱中表达,与CYP2As具有较高的氨基酸同一性,但未显示可检测到的ABP N-羟化酶活性。总之,尽管无法确定负责人膀胱微粒体中ABP N-羟基化的酶,但我们发现CYP2A13代谢激活ABP。

+1
+2
100研值 100研值 ¥99课程
检索文献一次
下载文献一次

去下载>

成功解锁2个技能,为你点赞

《SCI写作十大必备语法》
解决你的SCI语法难题!

技能熟练度+1

视频课《玩转文献检索》
让你成为检索达人!

恭喜完成新手挑战

手机微信扫一扫,添加好友领取

免费领《Endnote文献管理工具+教程》

微信扫码, 免费领取

手机登录

获取验证码
登录