Murray B P, Edwards R J, Murray S, Singleton A M, Davies D S, Boobis A R
Department of Clinical Pharmacology, Royal Postgraduate Medical School, London, UK.
Carcinogenesis. 1993 Apr;14(4):585-92. doi: 10.1093/carcin/14.4.585.
Mono-specific antibodies targeted to human CYP1A1 and CYP1A2 have been produced by immunizing rabbits with protein conjugates of short synthetic peptides corresponding to residues 290-297 and 284-296 respectively, of these enzymes. The antibody targeted to CYP1A1 bound in immunoblotting to the recombinant protein expressed in yeast but did not bind to any human hepatic microsomal protein, whereas the antibody targeted to CYP1A2 bound only to this enzyme in immunoblotting of human hepatic microsomal fractions and did not recognize recombinant human CYP1A1. The intensity of hepatic microsomal CYP1A2 immunoreactivity (n = 5) correlated significantly with a number of activities characteristic of this enzyme: phenacetin O-deethylase (POD), ethoxyresorufin O-deethylase (EROD) and methoxyresorufin O-demethylase activities and the ability to activate the dietary carcinogen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), to a mutagen. The anti-CYP1A2 anti-peptide antibody consistently inhibited both POD and EROD activities, but inhibition was incomplete (28%). In view of the known (> 90%) contribution of CYP1A2 to these activities and the correlation with antibody binding, this is consonant with an epitope for the anti-CYP1A2 anti-peptide antibody that forms the edge of a functionally important proinhibitory surface region previously identified in rat cytochromes CYP1A. CYP1A2 immunoreactivity determined by immunoblotting correlated significantly with the ability of human hepatic microsomal fractions to activate 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP), another dietary carcinogen, to a mutagen. It is concluded that CYP1A1 is absent from human liver and that CYP1A2 is likely to be a major catalyst in the hepatic activation of PhIP.
通过分别用与这些酶的第290 - 297位和第284 - 296位残基对应的短合成肽的蛋白质缀合物免疫兔子，制备了靶向人CYP1A1和CYP1A2的单特异性抗体。靶向CYP1A1的抗体在免疫印迹中与酵母中表达的重组蛋白结合，但不与任何人类肝微粒体蛋白结合，而靶向CYP1A2的抗体在人肝微粒体组分的免疫印迹中仅与该酶结合，不识别重组人CYP1A1。肝微粒体CYP1A2免疫反应性强度（n = 5）与该酶的一些特征活性显著相关：非那西丁O - 脱乙基酶（POD）、乙氧基试卤灵O - 脱乙基酶（EROD）和甲氧基试卤灵O - 脱甲基酶活性以及激活膳食致癌物2 - 氨基 - 3,8 - 二甲基咪唑[4,5 - f]喹喔啉（MeIQx）成为诱变剂的能力。抗CYP1A2抗肽抗体始终抑制POD和EROD活性，但抑制不完全（28%）。鉴于已知CYP1A2对这些活性的贡献> 90%以及与抗体结合的相关性，这与抗CYP1A2抗肽抗体的表位一致，该表位形成了先前在大鼠细胞色素CYP1A中鉴定的功能重要的前抑制表面区域的边缘。通过免疫印迹测定的CYP1A2免疫反应性与人肝微粒体组分激活另一种膳食致癌物2 - 氨基 - 1 - 甲基 - 6 - 苯基咪唑[4,5 - b]吡啶（PhIP）成为诱变剂的能力显著相关。结论是人类肝脏中不存在CYP1A1，并且CYP1A2可能是PhIP肝脏激活的主要催化剂。
