Inhibition and inactivation of constitutive cytochromes P450 in rat liver by parathion.
Inhibition and inactivation of constitutive cytochromes P450 in rat liver by parathion.
复制标题
对硫磷对大鼠肝脏中组成型细胞色素 P450 的抑制和灭活。
作者：
A. Butler;M. Murray
Phosphorothioate pesticides, such as parathion (O,O-diethyl-O-4-nitrophenyl phosphorothioate), undergo enzymic oxidation to the active insecticidal agents that are the analogous organophosphorus compounds. In hepatic microsomal fractions, the NADPH-mediated conversion of parathion to paraoxon occurs with concomitant loss of cytochrome P450 (P450) and associated activities. In this study, the capacity of parathion to inactivate specific P450 enzymes was studied in rat hepatic microsomes. Parathion was a potent inhibitor of P450 3A2- and 2C11-mediated androst-4-ene-3,17-dione (androstenedione) 6 beta- and 16 alpha-hydroxylation (Ki values of 13 +/- 2 and 2.3 +/- 0.1 microM, respectively, and Km/Ki ratios of 1.4 +/- 0.2 and 11 +/- 1, respectively). After a 10-min preincubation between parathion and NADPH-supplemented microsomes, to inactivate P450 before androstenedione hydroxylation was carried out, the corresponding Km/Ki ratios were increased to 3.5 +/- 0.4 and 35 +/- 6, reflecting 2.5- and 3.2-fold enhancement of inhibition of P450 3A2- and 2C11-dependent activities. In contrast to these findings, P450 2A1/2-mediated androstenedione 7 alpha-hydroxylation was refractory to inhibition and P450 2C6-mediated progesterone 21-hydroxylation was inhibited but not inactivated by the pesticide. Further studies established that androstenedione 6 beta- and 16 alpha-hydroxylation pathways were inactivated with maximal half-times of 2.59 min and 1.72 min, respectively. Although the incubation of parathion (50 microM) with rat liver microsomes for 10 min led to a 16% decrease in P450 estimated spectrophotometrically, immunoblot analysis revealed no change in the microsomal content of P450 2C11 apoprotein. Finally, NADPH-mediated metabolism of parathion to paraoxon (by desulfuration) and 4-nitrophenol (by oxidative cleavage of the phosphorothioate ester) occurred efficiently in microsomes (4.32 and 4.35 nmol/min/mg of protein, respectively). P450 loss was estimated under the same incubation conditions and, thus, 210 parathion molecules were oxidized for each molecule of holo-P450 lost. These findings establish that parathion is a potent inhibitor and inactivator of the principal constitutive P450s, 3A2 and 2C11, in rat liver, whereas the P450s 2A1 and 2A2 are refractory to either inhibition or inactivation. Another major constitutive enzyme, P450 2C6, is inhibited effectively by parathion but does not appear to be subject to inactivation.
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二氯甲基化合物作为体外大鼠肝细胞色素 P-450 的基于机制的灭活剂。
影响因子：
3.6
作者：
Halpert,JR;Balfour,C;Miller,NE;Kaminsky,LS
通讯作者：
Kaminsky,LS
在细胞色素 P-450 被破坏的各种反应中，与脱辅基蛋白的共价结合是血红素的主要命运。
DOI：
10.1016/0006-291x(86)90265-2
发表时间：
1986
影响因子：
3.1
作者：
Guengerich,FP
通讯作者：
Guengerich,FP
通过苯巴比妥诱导的大鼠肝脏细胞色素 P-450 同工酶测定自杀过程中烯丙基异丙基乙酰胺的分配比。
DOI：
--
发表时间：
1981
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Loosemore,MJ;Wogan,GN;Walsh,C
通讯作者：
Walsh,C
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影响因子：
3.6
作者：
Bornheim,LM;Underwood,MC;Caldera,P;Rettie,AE;Trager,WF;Wrighton,SA;Correia,MA
通讯作者：
Correia,MA
影响因子：
4.1
作者：
GUENGERICH, FP
通讯作者：
GUENGERICH, FP