ISOFORM-SELECTIVE MECHANISM-BASED INHIBITION OF HUMAN CYTOCHROME-P450 1A2 BY FURAFYLLINE
ISOFORM-SELECTIVE MECHANISM-BASED INHIBITION OF HUMAN CYTOCHROME-P450 1A2 BY FURAFYLLINE
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DOI：
10.1021/tx00035a009
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发表时间：
1993-09-01
影响因子：
4.1
通讯作者：
TRAGER, WF
中科院分区：
文献类型：
--
作者：
KUNZE, KL;TRAGER, WF
人类细胞色素P450 1A2 （P450 1A2）催化的生物转化反应似乎在药物的代谢清除和环境污染物和药物向有毒或致癌物质的活化中发挥重要作用。Furafylline是人肝微粒体P450 - 1A2活性的有效选择性抑制剂[Sesardic， D, Boobis, a ., Murray， B., Murray， S., Segura， J., De La Torre， R., and Davies， D. (1990) Br。j .中国。这可能对确定P450 - 1A2在代谢过程中的作用有很大的帮助。我们已经研究了furafylline是一种基于机制的P450 1A2抑制剂的假设。与这一假设一致的主要发现如下：(1)Furafylline导致P450 1A2活性的时间和辅助因子依赖性丧失，这种丧失在透析后不会恢复。(2)活性的丧失与P450光谱含量的降低有关，而P450光谱含量的降低又与来自7个个体肝脏的未抑制微粒体中P450 - 1a2相关的催化活性成正比。(3) P450 1A2失活的特征是K(i)为23 muM， K（inact）为0.87 min-1，基于呋喃茶碱消耗的分配比为每失活事件约3-6个代谢事件。(4)呋喃茶碱的C-8甲基参与了失活，氘同位素对k（inact）的影响约为2.0，而当呋喃茶碱的C-8甲基质子被氘原子取代时，对k(i)没有影响。(5)在所有P450 1A2活性被抑制的条件下，P450酶3A4和2C9的活性不受影响。Furafylline的效力、作用持久性和作用选择性表明，它可能是测定P450 1A2在药物和环境污染物处理中的作用的理想和独特的探针。
Biotransformation reactions catalyzed by human cytochrome P450 1A2 (P450 1A2) appear to play a significant role in both the metabolic clearance of drugs and the activation of environmental contaminants and drugs to toxic or carcinogenic species. Furafylline is a potent and selective inhibitor of P450 1A2 activity in human liver microsomes [Sesardic, D., Boobis, A., Murray, B., Murray, S., Segura, J., De La Torre, R., and Davies, D. (1990) Br. J. Clin. Pharmacol. 29, 651-663] which may be of great utility in defining the role of P450 1A2 in metabolic processes. We have investigated the hypothesis that furafylline is a mechanism-based inhibitor of P450 1A2. Key findings consistent with this hypothesis are the following: (1) Furafylline causes a time- and cofactor-dependent loss of P450 1A2 activity which does not return upon dialysis. (2) The loss of activity is associated with a reduction of P450 spectral content which is in turn proportional in amount to P450 1A2-associated catalytic activity in uninhibited microsomes from 7 individual livers. (3) The inactivation of P450 1A2 is characterized by a K(i) of 23 muM, a k(inact) of 0.87 min-1 and a furafylline depletion-based partition ratio of approximately 3-6 metabolic events per inactivating event. (4) The processing of the C-8 methyl group of furafylline is involved in inactivation as demonstrated by the observation of a deuterium isotope effect of approximately 2.0 on k(inact) and no effect on K(i) when the C-8 methyl group protons of furafylline are replaced with deuterium atoms. (5) Under conditions in which all P450 1A2 activity is inhibited, the activities of the P450 enzymes 3A4 and 2C9 are unaffected. Furafylline's potency, persistence of effect, and selectivity of action suggest that it may be an ideal and unique probe for determination of the role of P450 1A2 in the processing of drugs and environmental contaminants.