Hydroxylation of benzo[a]pyrene and binding of (-)trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene metabolites to deoxyribonucleic acid catalyzed by purified forms of rabbit liver microsomal cytochrome P-450. Effect of 7,8-benzoflavone, butylated hydroxytoluene and ascorbic acid.
Hydroxylation of benzo[a]pyrene and binding of (-)trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene metabolites to deoxyribonucleic acid catalyzed by purified forms of rabbit liver microsomal cytochrome P-450. Effect of 7,8-benzoflavone, butylated hydroxytoluene and ascorbic acid.
复制标题
纯化形式的兔肝微粒体细胞色素 P-450 催化苯并[a]芘的羟基化以及 (-)trans-7,8-二羟基-7,8-二氢苯并[a]芘代谢物与脱氧核糖核酸的结合。
DOI：
10.1016/0006-2952(80)90127-6
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发表时间：
1980
影响因子：
5.8
通讯作者：
H. Gelboin
中科院分区：
文献类型：
--
作者：
Giorgio Belvedere;Haruko Miller;K. P. Vatsis;M. J. Coon;H. Gelboin
未处理、苯巴比妥处理和3-甲基胆蒽处理的成年兔肝微粒体对苯并[a]芘羟基化和（-）（反式-7，8-二羟基-7，8-二氢苯并[a]芘[（−）反式-7，8-二醇]与DNA结合代谢物的关系，功能氧化酶抑制剂，并与相应的活性的个别酶系统。用苯巴比妥处理兔子导致P-450 LM 2的诱导和微粒体苯并[a]芘羟化酶活性的3倍增强，而（-）反式-7，8-二醇转化为DNA结合产物不受影响。均相苯巴比妥诱导的P-450 LM 2对苯并[a]芘表现出最高的活性和特异性，对（-）反式-7，8-二醇表现出最低的活性。相反，P-450 LM 4是3-甲基胆蒽或β-萘啶酮诱导的兔肝细胞色素P-450的主要形式，这与微粒体中（-）反式-7，8-二醇代谢的增加有关，但与苯并[a]芘无关。均相P-450 LM 4优先催化（−）trans-7，8-diol的氧化，但对苯并[a]芘基本无效。部分纯化的P-450 LM 7缺乏底物特异性，因为它以相当的速率代谢苯并[a]芘和（-）反式-7，S-二醇。此外，7，8-benzodiazone强烈抑制P-450 LM 4和苯巴比妥诱导的微粒体对苯并[a]芘的羟基化，以及P-450 LM 4和3-甲基胆蒽诱导的微粒体对（−）反式-7，8-二醇的代谢;相反，对照微粒体与任一底物的活性，以及P-450 LM 4和LM 2分别与苯并[a]芘和（-）反式-7，8-二醇的活性，仅部分或轻微降低7，8-benzodiazone。与7，8-苯并吡喃酮不同，丁基化羟基甲苯仅抑制苯并[a]芘羟基化。因此，不同形式的兔肝微粒体细胞色素P-450参与苯并[a]芘及其7，8-二氢二醇的代谢。结果还表明，在苯巴比妥和3-甲基胆蒽诱导的微粒体中观察到的底物特异性和抑制剂敏感性相对于对照兔肝微粒体的变化可以通过这些制剂中普遍存在的细胞色素P-450的特定形式P-450 LM 2和LM 4的催化特性来解释。
The catalytic activities of hepatic microsornes from untreated, phenobarbital-treated and 3-methylcholanthrene-treated adult rabbits with respect to benzo[a]pyrene hydroxylation and the activation of (−)(rflw-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene[(−)trans-7,8-diol] to DNA-binding metabolites were determined in the absence and presence of mixed-function oxidase inhibitors and compared to the corresponding activities of the individual enzyme systems. Treatment of rabbits with phnobarbital led to induction of P-450LM2and a concomitant 3-fold enhancement in microsomal benzo[a]pyrene hydroxylase activity, whereas the conversion of (−)trans-7,8-diol to DNA-binding products was unaffected. Homogeneous phenobarbital-inducible P-450LM2exhibited the highest activity and specificity toward benzo[a]pyrene and the lowest activity toward (−)trans-7,8-diol. Conversely, P-450LM4was the major form of cytochrome P-450 induced in rabbit liver by 3-methylcholanthrene or β-naphthoflavone, and this was associated in microsomes with an increase in the metabolism of (−)trans-7, 8-diol but not of benzo[a]pyrene. Homogeneous P-450LM4preferentially Catalyzed the oxygénation of (−)trans-7,8-diol, but was largely ineffective with benzo[a]pyrene. Partially purified P-450LM7lacked substrate specificity, for it metabolized both benzo[a]pyrene and (−)trans-7, S-diol at comparable rates. Additionally, 7,8-benzoflavone strongly inhibited benzo[a]pyrene hydroxylation by P-450LM4and phenobarbital-induced microsomes, as well as (−)trans-7,8-diol metabolism by P-450LM4and 3-methyl-cholanthrene-induced microsomes; in contrast, the activity of control microsomes with either substrate, and the activities of P-450LM4and LM2with benzo[a]pyrene and (−)trans-7 ,8-diol, respectively, were only partially or slightly decreased by 7,8-benzoflavone. Unlike 7,8-benzoflavone, butylated hydroxytoluene inhibited benzo[a]pyrene hydroxylation only. Thus, different forms of rabbit liver microsomal cytochrome P-450 were involved in the metabolism of benzo[a]pyrene and its 7,8-dihydrodiol. The results also demonstrate that the changes in substrate specificity and inhibitor sensitivity seen in phenobarbital- and 3-methylcholanthrene-induced microsomes relative to control rabbit liver microsomes can be accounted for by the catalytic properties of a specific form of cytochrome P-450 that prevails in these preparations, P-450LM2and LM4, respectively.