Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aim of this study was to clarify the mechanism by which cytochrome P450 (P450)-mediated catalytic activity is decreased following interferon (IFN) administration. Microsomal steroid hydroxylation was assessed to test the hypothesis that IFN selectively decreases the activities of individual P450 isozymes in male rats. Thus, recombinant rat IFN gamma (r-rat IFN gamma) treatment produced 40% and 17% reductions in androst-4-ene-3,17-dione (androstenedione) 6 beta- and 16 beta-hydroxylation, respectively. Androstenedione 16 alpha- and 7 alpha-hydroxylation were unaltered following r-rat IFN gamma treatment. Similar changes in the androstenedione hydroxylation pathways were observed following administration of naturally derived rat IFN alpha/beta. Microsomal levels of P450IIIA2, the male-specific constitutive steroid 6 beta-hydroxylase, were lower after administration of r-rat IFN gamma (42% of control fractions). Furthermore, hepatic P450IIIA2 mRNA was found to be decreased to a similar extent by r-rat IFN gamma. These findings suggest that IFN selectively decreases the content of this isozyme by a mechanism involving altered mRNA regulation. Sex steroids were unlikely to have mediated the decrease in P450IIIA2 levels since serum estradiol and testosterone levels were unchanged by r-rat IFN gamma. In order to determine whether IFN alters the expression of P450IIIA1, a steroid-inducible member of the P450IIIA gene subfamily which is not expressed in untreated rat liver, adult female rats (which lack P450IIIA2) were coadministered pregnenolone 16 alpha-carbonitrile and r-rat IFN gamma. However, IFN failed to impair the induction of androstenedione 6 beta-hydroxylation produced by pregnenolone 16 alpha-carbonitrile. These findings suggest that although IFN decreases the expression of P450IIIA2, it may not down regulate the expression of other steroid-inducible P450IIIA proteins. In view of the existence of human P450IIIA orthologs which catalyze the metabolism of several important therapeutic agents, the findings of this study may help predict possible drug interactions in patients receiving IFN.
Mol Pharmacol 1990 Sep
PMID:Interferon down regulates the male-specific cytochrome P450IIIA2 in rat liver. 169 50

The substrate recognition regions in cytochrome P450 family 2 (CYP2) proteins were inferred by group-to-group alignment of CYP2 sequences and those of bacterial P450s, including Pseudomonas putida P450 101A (P450cam), whose substrate-binding residues have been definitely identified by x-ray crystallography of a substrate-bound form (Poulos T. L., Finzel, B. C., and Howard, A. J. (1987) J. Mol. Biol. 195, 687-700). The six putative substrate recognition sites, SRSs, thus identified are dispersively located along the primary structure and constitute about 16% of the total residues. All the reported point mutations and chimeric fragments that significantly affect the substrate specificities of the parental CYP2 enzymes fell within or overlapped some of the six SRSs. Analysis of nucleotide substitution patterns in closely related members in four subfamilies, CYP2A, 2B, 2C, and 2D, consistently indicated that the SRSs have accumulated more nonsynonymous (amino acid-changing) substitutions than the rest of the sequence. This observation supports the idea that diversification of duplicate genes of drug-metabolizing P450s occurs primarily in substrate recognition regions to cope with an increasing number of foreign compounds.
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PMID:Substrate recognition sites in cytochrome P450 family 2 (CYP2) proteins inferred from comparative analyses of amino acid and coding nucleotide sequences. 173 Jun 27

This study was conducted to explore the potency of morphine to induce reductions of specific cytochrome P450 isoenzyme functions. Male Sprague-Dawley rats were treated with escalating doses (20-125 mg/kg per day) of morphine for 2 weeks in order to study the effects on the following cytochrome P450 catalyzed reactions: 16 alpha-hydroxylation of dehydroepienderosterone (DHA) and progesterone; 17 alpha- and 21-hydroxylation of progesterone; N-demethylation of ethymorphine, codeine and morphine as well as O-dealkylation of ethylmorphine and codeine. 16 alpha-Hydroxylation of DHA and progesterone and 17 alpha-hydroxylation of progesterone decreased to 18, 12 and 10% of control activities, respectively. The N-demethylation of ethylmorphine and codeine decreased to 34 and 43% of control activities, respectively. Morphine treatment had no effect on the 21-hydroxylation reactions or the O-dealkylation of ethylmorphine or codeine. A monoclonal antibody (Mab) against rat liver cytochrome P450 2 c/RLM 5 exerted a 66-73% inhibition of the N-demethylation of ethylmorphine and codeine, respectively, whereas the O-dealkylation reactions were not affected. This Mab inhibited the 16 alpha- and 17 alpha-hydroxylation of DHA and progesterone, whereas the 21-hydroxylation reactions were unaffected. The steroid hydroxylation reactions in rat adrenals were not altered upon morphine treatment. Our data suggest that a major part of the 16 alpha- and 17 alpha-steroid hydroxylations are catalyzed by the same (or closely related) cytochrome(s) P450 as the opioid N-demethylation reactions.
J Steroid Biochem Mol Biol 1992 Jan
PMID:A conspicuous down-regulating effect of morphine on essential steroid hydroxylation reactions and certain drug N-demethylations. 173 39

Many species within the order Actinomycetales contain one or more soluble cytochrome P450 monooxygenases, often substrate-inducible and responsible for a variety of xenobiotic transformations. The individual cytochromes exhibit a relatively broad substrate specificity, and some strains have the capacity to synthesize large amounts of the protein(s) to compensate for low catalytic turnover with some substrates. All three of the Streptomyces cytochromes sequenced to date are exclusive members of one P450 family, CYP105. In several instances, monooxygenase activity arises from induction of a P450 and associated ferredoxin, or of a P450 only, suggesting that some essential electron donor proteins (reductase and ferredoxin) are not co-ordinately regulated with the cytochrome. The overall properties of these systems suggest an adaptive strategy whose twofold purpose is to maintain a competitive advantage via the production of secondary metabolites, and, whenever possible, to utilize unusual growth substrates by introducing metabolites from these reactions into the more substrate-specific primary metabolic pathways.
Mol Microbiol 1991 Sep
PMID:Occurrence and biological function of cytochrome P450 monooxygenases in the actinomycetes. 176 83

This study examined various biochemical parameters such as mitochondria and mitochondrial DNA (mtDNA), total heme and cyto P450 content in fresh hepatocytes and dedifferentiated hepatocytes. These parameters were chosen in order to understand the dramatic decrease in drug metabolism in cultured hepatocytes. The data in this study shows a temporal decrease in cytochrome P450, a total heme and also a decrease in mitochondria. Also, the ratio of mtDNA content to mitochondrial density was found to increase as hepatocytes underwent dedifferentiation. Stereological analysis of cell preparations provided a measure of mitochondrial density per cell area and mtDNA content was assessed by the use of a specific radiolabelled probe. This study demonstrates that a loss of the organelle which is partially responsible for synthesis of heme correlates with a decrease in cytochrome P450.
Mol Cell Biochem 1991 Dec 11
PMID:A mechanism for the loss of cytochrome P-450 in primary mouse hepatocytes. 177 61

The expression and molecular regulation of the cytochrome P450IA (P450IA) gene subfamily have been examined in rat hepatic tissue after treatment with pyridine. The microsomal ethoxyresorufin O-deethylase activity, which has been shown to be specific for the P450IA subfamily, was increased approximately 2- and 3.5-fold over control values at 10 and 16 hr, respectively, after a single dose of pyridine (100 mg/kg, intraperitoneally). P450IA1 protein expression was also elevated in a time-dependent manner, with a maximal increase in P450IA1 protein being seen at approximately 16 hr after a single dose of pyridine (100 mg/kg, intraperitoneally), as detected by immunoblot analysis using a monoclonal antibody that detects both P450IA1 and P450IA2. The immunochemically detectable level of P450IA1 decreased to that of control at 48 hr after treatment. Oligonucleotide probes specific for P450IA1 and P450IA2 mRNA were used in hybridization analyses to examine mRNA levels of P450IA1 and P450IA2, respectively. The level of P450IA1 mRNA in poly(A)+ mRNA was increased approximately 3- and 2-fold at 5 and 12 hr, respectively, after a single injection of pyridine, as evidenced by both slot blot and Northern blot analyses. A lesser increase (approximately 1.5-2-fold) in P450IA2 mRNA was also seen at 5 and 12 hr after treatment. The P450IA1 and P450IA2 mRNA levels returned to control values at 48 hr after pyridine administration. These results were compared with those produced by 3-methylcholanthrene at 5 hr after treatment. A multiplex polymerase chain reaction assay was also used to monitor simultaneously the changes in P450IA1, P450IA2, and P450IIE1 mRNA levels, and the results showed induction of P450IA1, in agreement with the results of slot and Northern blot analyses. In summary, metabolic activity assays, immunochemical detection, and Northern and slot blot analyses provide evidence to support the conclusion that pyridine modulates the expression of the P450IA gene subfamily and does so by elevating P450IA1 and P450IA2 mRNAs, through either transcriptional activation or increased mRNA stabilization. These results are in sharp contrast to P450IIE1 induction by pyridine, which appears to proceed through increased translational efficiency. Thus, pyridine, which is present in tobacco and tobacco smoke, is capable of simultaneously elevating multiple forms of P450 that are active in carcinogen metabolism.
Mol Pharmacol 1991 Jul
PMID:Pyridine effects on expression and molecular regulation of the cytochrome P450IA gene subfamily. 185 40

The monoclonal antibody MAb 1-68-11, prepared to constitutive cytochrome P450 IIC11 (2c/RLM5) from male Sprague-Dawley rat liver, was used to study the contribution of the class of cytochrome P450s epitopically related to P450 IIC11 to the regiospecific metabolism of benzo[a]pyrene (BP) and its binding to DNA. The effect of MAb 1-68-11 was determined on the conversion of BP to BP-9,10-dihydrodiol, BP-7,8-dihydrodiol, BP-4,5-dihydrodiol, BP phenols, and BP quinones, and on the P450-dependent DNA binding catalyzed by P450 in microsomes from uninduced male and female Wistar and Sprague-Dawley rat livers, as well as 3-methylcholanthrene- and phenobarbital (PB)-induced male Wistar rat livers. In liver microsomes from untreated male rats, MAb 1-68-11 inhibited BP-9,10-dihydrodiol formation by 80%; in liver microsomes from untreated female rats, the inhibition was 100%. BP-7,8-dihydrodiol formation was inhibited from 38 to 77% in microsomes from males and 50% in those from females. In microsomes from PB-induced rats, inhibition of the 9,10-dihydrodiol and the 7,8-dihydrodiol was 90% and 73%, respectively, whereas BP-4,5-dihydrodiol formation was enhanced 80%. In microsomes from 3-methylcholanthrene-treated rats, no inhibition of MAb 1-68-11 was observed on either the metabolism of BP or its binding to DNA. In contrast, the binding of BP to DNA was completely inhibited by MAb 1-68-11 in microsomes from uninduced male Wistar rats and 70% in PB-induced microsomes. 32P-postlabeling analysis showed that formation of the major stable adduct, BP diol epoxide bound at C-10 to the 2-amino of deoxyguanosine, was strongly inhibited in uninduced and PB-induced microsomes. Formation of the major labile BP-DNA adduct 7-(benzo[a]pyren-6-yl) guanine (BP-N7Gua) was inhibited about 60% in microsomes from untreated male Wistar rats. These results show that MAb 1-68-11 regiospecifically inhibits cytochrome P450 IIC11 and epitopically related P450s that metabolize BP at the 7,8 and 9,10 positions. MAb 1-68-11 also inhibits enzyme-catalyzed binding of BP to DNA in the specific formation of BP-N7Gua and adducts detected by the 32P-postlabeling technique.
Mol Carcinog 1991
PMID:A monoclonal antibody to rat liver cytochrome P450 IIC11 strongly and regiospecifically inhibits constitutive benzo[a]pyrene metabolism and DNA binding. 187 51

In rats, cytochrome P450 (P450) IIIA enzymes are an important determinant of digitoxin toxicity. Induction of these liver microsomal enzymes decreases the toxicity of digitoxin by increasing its oxidative cleavage to digitoxigenin bis- and monodigitoxoside (dt2 and dt1). The present study shows that the susceptibility of different mammalian species to digitoxin toxicity is inversely related to liver microsomal P450 IIIA activity (measured as testosterone 6 beta-hydroxylase activity). Based on this correlation, we correctly predicted that hamsters, which have the highest P450 IIIA activity, are extremely resistant to digitoxin toxicity. To further examine the relationship between digitoxin toxicity and P450 IIIA activity, the pathways of digitoxin metabolism catalyzed by liver microsomes from nine mammalian species were examined by high performance liquid chromatography. The overall rate of digitoxin metabolism varied approximately 90-fold and followed the rank order: hamster greater than rat greater than guinea pig greater than dog greater than mouse approximately monkey greater than rabbit approximately cat greater than human. The qualitative differences in digitoxin metabolism were as striking as the quantitative differences. Formation of 16- and/or 17-hydroxydigitoxin was the major pathway of digitoxin oxidation catalyzed by liver microsomes from hamster, guinea pig, rabbit, cat, dog, and cynomolgus monkey. Guinea pig and, to a lesser extent, hamster liver microsomes also converted digitoxin to an unknown metabolite, the formation of which was catalyzed by P450. None of the species examined catalyzed the 12-hydroxylation of digitoxin to digoxin at a high rate. Similarly, none of the species examined catalyzed a high rate of conversion of digitoxin to dt2, with the notable exception of the rat. However, dt2 formation was the major pathway of digitoxin metabolism catalyzed by human liver microsomes, although humans were much less active (approximately 2%) than rats in this regard. The rate of dt2 formation varied approximately 41-fold among 22 samples of human liver microsomes, which was highly correlated (r = 0.841) with the rate of testosterone 6 beta-hydroxylation. Antibody against rat P450 IIIA1 inhibited the high rate of dt2 formation by rat liver microsomes and the low rate catalyzed by mouse, guinea pig, dog, monkey, and human liver microsomes. In contrast, anti-P450 IIIA1 did not inhibit the 12-, 16-, or 17-hydroxylation of digitoxin (or the formation of the unknown metabolite), despite the fact that anti-P450 IIIA1 strongly inhibited (greater than 70%) the 6 beta-hydroxylation of testosterone by liver microsomes from each of the species examined (except rabbit liver microsomes, which were inhibited only approximately 30%).(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Pharmacol 1991 Nov
PMID:Species differences in the toxicity and cytochrome P450 IIIA-dependent metabolism of digitoxin. 194 47

Monooxygenases in the cytochrome P450 IIIA subfamily are induced by a number of their xenobiotic substrates and by testosterone, an endobiotic substrate of importance in their regulation. 17 alpha-Ethinylestradiol (EE) is also metabolized by these enzymes and in this study Dark Agouti rats were used to examine the effects of subcutaneous implantation of controlled release silastic capsules containing EE to determine if this steroid also induces these enzymes. Data were compared with results obtained from equivalent groups of animals implanted with capsules containing testosterone propionate (TP). Liver microsomes prepared from male and female rats were used to identify intrinsic gender differences in the monooxygenases studied and gender differences in the responses to the implanted steroids were also determined. Effects due to imprinting of growth hormone secretion patterns were controlled by using male and female birth gonadectomized animals. Results obtained from groups with blank implants showed there were no effects due to the silastic implant material itself on the monooxygenases studied. The specific activities of erythromycin N-demethylation in liver microsomes of both EE and TP implanted male and female birth gonadectomized animals were enhanced relative to corresponding blank implanted controls consistent with both steroids having an effect to induce activity attributable to cytochrome P450 IIIA isoforms. Immunoinhibition studies using microsomes from EE treated female rats with erythromycin as substrate provided further evidence for this steroid having this induction effect. The specific activity of ethylmorphine N-demethylation was however not increased in microsomes prepared from the EE implanted female animals and was decreased in the corresponding male preparations. These findings distinguished the response to this steroid from that to TP and suggested induction by this estrogen of an isoform(s) having a more limited range of substrates than has characteristically been found in this subfamily. EE treatment also caused an increase in diazepam C3 hydroxylase consistent with an effect to induce P450 IIIA activity but this was found only in microsomes from birth gonadectomized female animals. This was in contrast to the effect of TP treatment which produced increases in this monooxygenase in both male and female animals. Another gender specific effect of EE was a striking decrease in morphine N-demethylase activity seen only in birth gonadectomized male rats. This again contrasted with the effect of TP which caused a marked increase in this activity in liver microsomes of both male and female birth gonadectomized animals consistent with the proposal that testosterone is important in the regulation of this activity.(ABSTRACT TRUNCATED AT 400 WORDS)
J Steroid Biochem Mol Biol 1991 Nov
PMID:Effects of ethinylestradiol and testosterone implants on hepatic microsomal cytochrome P450 monooxygenases of birth gonadectomized male and female Dark Agouti rats. 195 10

In recent years it has become apparent that tropic hormones involved in steroidogenesis act to regulate the expression of the enzymes involved in the various steroidogenic pathways. This is particularly evident in the ovary where the episodic secretion of steroids throughout the ovarian cycle is regulated largely by changes in the levels of the particular enzymes involved in each step of the steroid biosynthetic pathways. Recently, the genes for the various cytochrome P450 species involved in ovarian steroidogenesis, namely cholesterol side-chain cleavage P450 (P450SCC), 17 alpha-hydroxylase P450 (P450(17 alpha], and aromatase cytochrome P450 (P450AROM) have been isolated and characterized, making it possible to study the regulation of expression at the molecular level. To this end, a series of chimeric constructs have been prepared in which fragments of the 5'-untranslated region of bovine P450(17 alpha) and P450SCC have been inserted upstream of the chloramphenicol acetyl transferase (CAT) and beta-globin reporter genes. These constructs have been used to transfect primary cultures of bovine luteal and thecal cells. The results indicate that cAMP responsiveness lies within defined regions of genes which do not contain a classical CRE, similar to previous results utilizing adrenal cells in culture. Furthermore, although constructs containing both the P450(17 alpha) and P450SCC 5'-upstream regions are expressed in both luteal and thecal cell cultures, only those containing the P450SCC sequences are expressed in luteal cells. Studies on the expression of P450AROM indicate that the promoter which is responsible for its expression in human placenta is not operative in the corpus luteum. Thus estrogen biosynthesis may be regulated by the differential use of tissue specific promoters, thus accounting for the complexity and multifactorial nature of the expression of this activity.
J Steroid Biochem Mol Biol 1991
PMID:Regulation of expression of the genes encoding steroidogenic enzymes. 195 46


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