<i>N</i>-Nitrosobenzylmethylamine Hydroxylation and Coumarin 7-Hydroxylation: Catalysis by Rat Esophageal Microsomes and Cytochrome P450 2A3 and 2A6 Enzymes
作者:Linda B. von Weymarn、Nadia D. Felicia、Xinxin Ding、Sharon E. Murphy
DOI:10.1021/tx990128y
日期:1999.12.1
respectively. Both enzymes catalyzed methylene hydroxylation at least 4-fold more efficiently than methyl hydroxylation. In addition, P450 2A6, but not P450 2A3, catalyzed benzyl ring hydroxylation, generating N-(p-hydroxybenzyl)methylamine. The identity of this metabolite was confirmed by synthesis of a standard and LC/MS and LC/MS/MS analysis. P450 2A6 is an efficient coumarin 7-hydroxylase, and
N-亚硝基苄基甲胺(NBzMA)是大鼠中一种有效的选择性食道致癌物,可能是人类食道癌的病原体。像大多数亚硝胺一样,该亚硝胺必须被代谢活化才能发挥其致癌潜力。NBzMA可以通过P450催化的甲基或亚甲基羟基化来代谢;后者被认为是激活途径。据信食管对NBzMA诱导的肿瘤发生的敏感性至少部分归因于该组织中存在有效的P450催化剂。然而,尽管将近20年前曾报道过大鼠食道可催化NBzMA的亚甲基羟基化反应,但催化该反应的P450尚未确定。我们在这里报告人类P450 2A6和密切相关的肝外大鼠酶P450 2A3都有效地催化NBzMA亚甲基羟基化,表征为苯甲醛的形成。P450 2A3在该反应中的催化效率是P450 2A6的三倍,为7.6(K(m)= 0.63 +/- 0.18 microM,V(max)= 4.8 nmol min(-)(1)nmol P450(-)(1))相对于2.3(K(m)= 6.7