代谢
人类细胞色素P450 1A2在外源化学物质代谢中催化重要的反应,包括致癌芳香胺的N-羟基化。2001年,Chevalier等人报道了人类群体中四个新的P450 1A2序列变异...这些变异在大肠杆菌中得到了表达,并对蛋白质表达(全酶的光谱测量和免疫印迹)以及IQ(2-氨基-3-甲基咪唑[4,5-f]喹啉)和MeIQ(2-氨基-2,4-二甲基咪唑[4,5-f]喹啉)在lacZ回复突变试验中的生物活化进行了测量。对五种杂环胺底物的N-羟基化以及非那西汀的O-脱乙基化进行了酶动力学分析。R431W替换产生了最显著的影响:没有检测到全酶。这个残基位于“螺旋”肽区域,早期的定点突变研究表明它对维持蛋白质的三级结构至关重要。其他三个变异与野生型酶相比具有细微不同的催化活性。
Human cytochrome P450 1A2 catalyzes important reactions in xenobiotic metabolism, including the N-hydroxylation of carcinogenic aromatic amines. In 2001, Chevalier et al. reported four new P450 1A2 sequence variants in the human population ...These variants /have been expressed/ in Escherichia coli and protein expression (optical spectroscopy of holoenzyme and immunoblotting) and bioactivation of IQ (2-amino-3-methylimidazo[4,5-f]quinoline) and MeIQ (2-amino-2,4-dimethylimidazo[4,5-f]quinoline) in the lacZ reversion mutagenicity test /were measured/. Enzyme kinetic analyses were performed for N-hydroxylation of five heterocyclic amine substrates and for O-deethylation of phenacetin. The most drastic effect was that of the R431W substitution: no holoenzyme was detectable. This residue is located in the "meander" peptide region and earlier site-directed mutagenesis studies demonstrated that it is critical for maintenance of protein tertiary structure. The other three variants had subtly different catalytic activities compared to the wild-type enzyme.
来源:Hazardous Substances Data Bank (HSDB)