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 genotoxicity of the terpene beta-myrcene was evaluated in mammalian cells in vitro. Myrcene is the major constituent of oil of bay and hop which are used in the manufacture of alcoholic beverages. Myrcene is also present in lemon grass (Cymbopogon citratus), a plant widely used in Brazilian folk medicine. Recently, it was shown that myrcene is a very potent analgesic substance and might be an alternative to the already available analgesic drugs. Myrcene was tested up to 1,000 micrograms/ml (limit of solubility) in the presence and absence of S9-mix and did not induce chromosome aberrations and sister chromatid exchanges (SCEs) in human lymphocytes in vitro. Neither the mitotic index nor the proliferation index was influenced by the myrcene treatment. Myrcene did not cause increased mutation frequencies at the hprt-locus in V79-cells. Tests with and without S9-mix revealed negative results. There was no indication for induced cytotoxicity. However, myrcene reduced the SCE-inducing effect of cyclophosphamide in human lymphocytes in a dose dependent manner and also reduced the toxic and mutagenic effect of cyclophosphamide in V79-cells. Under the same test conditions, SCE induction by ethyl methanesulfonate (EMS) and benzo [a]pyrene (BP) was not significantly influenced by simultaneous myrcene treatment. The in vitro results show that myrcene is not mutagenic in mammalian cells, but has antimutagenic properties. The possibility that myrcene exerts its antimutagenic activity by inhibiting certain forms of the cytochrome P-450 isoenzymes required for activation of premutagens and precarcinogenes is discussed.
Environ Mol Mutagen 1991
PMID:Evaluation of the mutagenicity of beta-myrcene in mammalian cells in vitro. 186 66

Previous investigations have established that spironolactone (SL) is converted to a reactive metabolite by adrenal microsomal enzymes, resulting in the degradation of cytochrome P-450 (P-450). Deacetylation of SL to 7 alpha-thiospironolactone (7 alpha-thio-SL) is the first step in the activation pathway, but further NADPH-dependent metabolism of 7 alpha-thio-SL is required for P-450 destruction. Studies were done to evaluate the role of the steroid 17 alpha-hydroxylase in the activation of 7 alpha-thio-SL by adrenal microsomes. Incubation of guinea pig adrenal microsomes with 7 alpha-thio-SL in the presence of NADPH effected greater than 50% declines in P-450 content and in 17 alpha-hydroxylase activity but no change in the rate of 21-hydroxylation. Preincubation of the microsomes with antisera to the 17 alpha-hydroxylase P-450 isozyme (P-450(17 alpha,lyase)) decreased 17 alpha-hydroxylase but not 21-hydroxylase activity and prevented the degradation of P-450 by 7 alpha-thio-SL. Control IgG had no effect on 17 alpha-hydroxylase activity or on the 7 alpha-thio-SL-mediated destruction of P-450. When added to a purified P-450(17 alpha,lyase) preparation, 7 alpha-thio-SL and the endogenous substrate progesterone caused typical type I spectral changes, but SL did not. Incubation of a purified and reconstituted 17 alpha-hydroxylase system, consisting of P-450(17 alpha,lyase), NADPH-P-450 reductase, cytochrome b5, and dilauroylphosphatidylcholine, with 7 alpha-thio-SL plus NADPH effected the complete degradation of the P-450(17 alpha,lyase). Neither progesterone nor SL caused P-450 destruction with the reconstituted enzyme preparation. The results provide direct evidence for the activation of 7 alpha-thio-SL by the 17 alpha-hydroxylase and support the hypothesis that a mechanism-based inhibition of the enzyme occurs. The data also provide additional evidence that 7 alpha-thio-SL is an obligatory intermediate in the degradation of P-450 by SL.
Mol Pharmacol 1991 Aug
PMID:Role of the steroid 17 alpha-hydroxylase in spironolactone-mediated destruction of adrenal cytochrome P-450. 187 14

Ascorbic acid (VC) deficiency resulted in a decrease in the activities of aminopyrine N-demethylase, aniline hydroxylase, and p-nitroanisole O-demethylase and in the content of cytochrome P-450, as spectrally determined, whereas it caused an increase in the activities of 6 beta-hydroxylases for testosterone and progesterone in liver microsomes of guinea pigs. Western blot analysis of liver microsomes with antibodies to rat P-448-H (P-4501A2), P-450j (P-450IIE), P-450 PB-1 (P-450IIIA), and P-450b (P-450IIB1) showed that VC deficiency decreased the amount of cytochrome P-450 immunochemically related to P-450IA2 and P-450IIE but did not change the amount of the form that was cross-reactive with antibodies to P-450IIB1 and tended to slightly increase (not statistically significantly) the amount of the form of the cytochrome immunochemically related to P-450IIIA. The larger decrease by VC deficiency in the amount of cytochrome P-450 that was cross-reactive to the rat P-450IA2 resulted in a lower capacity of liver microsomes to activate promutagens, such as 2-amino-3-methyl-imidazo(4,5-f)quinoline and aflatoxin B1. These results indicate that VC deficiency in guinea pigs differentially affects the content of individual forms of cytochrome P-450.
Mol Pharmacol 1991 Apr
PMID:Ascorbic acid deficiency decreases specific forms of cytochrome P-450 in liver microsomes of guinea pigs. 190 38

The alcohol-inducible CYP2E subfamily in rabbits contains two genes; CYP2E1 encodes the cytochrome earlier termed P-450 3a, and CYP2E2 encodes a cytochrome that is 97% identical in amino acid sequence to cytochrome P-450 (P-450) 2E1. In the present studies, the ontogenic expression of these two cytochromes was examined. In liver, P-450 2E2 mRNA is detectable immediately after birth and reaches slightly greater than the adult level at 2 weeks of age; in contrast, P-450 2E1 mRNA is not detectable until day 14 and increases rapidly to approximately twice the adult level at 5 weeks of age. P-450 2E protein is present in liver immediately after birth, coincident with the appearance of P-450 2E2 mRNA, peaks at 2 weeks, and then, despite the continued elevation in P-450 2E mRNA, decreases to the adult level at 5 weeks. In kidney, P-450 2E2 mRNA is not detectable at any age; P-450 2E1 mRNA, however, is present at 1 week, and the level increases to about half the adult level at 5 weeks of age. P-450 2E protein in this tissue is elevated at 2 weeks, relative to mRNA levels, and reaches approximately half the adult level at 5 weeks. The lack of close correlation between mRNA and protein levels in the liver and kidney of newborn rabbits indicates that the posttranscriptional control of P-450 2E enzyme levels that predominates in adult animals is also operative during the neonatal period. Monooxygenase activities with ethanol and p-nitrophenol as substrates reflect the developmental increase in P-450 2E protein, as well as the appearance and levels of spectrally detectable P-450, cytochrome b5, and NADPH-P-450 reductase in hepatic microsomes. The expression of P-450 2E2, but not P-450 2E1, in early neonates suggests that these two closely related cytochromes may have functional differences that are important during the first few weeks of life.
Mol Pharmacol 1991 Jul
PMID:Differences in the developmental expression of rabbit cytochromes P-450 2E1 and 2E2. 190 76

Estrogen synthetase (aromatase) is a cytochrome P-450 enzyme system which converts androgens to estrogens. Although this enzyme has been purified and the cDNA-derived amino acid sequence elucidated, very little is known regarding post-translational modifications of this physiologically crucial enzyme. We show here that the cytochrome P-450 component, P-450ES, purified from human term placental microsomes, is a glycoprotein based on the following evidence: its molecular weight is decreased following treatment with endoglycosidase F, concanavalin A-biotin specifically binds to this protein immobilized on nitrocellulose, and its oligosaccharide composition is consistent with a single N-linked fucosylated complex type carbohydrate chain. In a reconstitution system, the aromatase activity using the endoglycosidase F-treated P-450ES was reduced by about 35-40% relative to the native form, regardless of whether androstenedione or testosterone was used as substrate.
Mol Cell Endocrinol 1991 Jun
PMID:Estrogen synthetase (aromatase). The cytochrome P-450 component of the human placental enzyme is a glycoprotein. 193 23

Steroid 17 alpha-hydroxylase has emerged as a key enzyme in steroidogenic cells: (i) it represents the branch point between the 17-deoxy (mineralo) and the 17-hydroxy (gluco) corticosteroid pathways in the adrenal cortex; (ii) the corresponding specific cytochrome (P-450(17 alpha] is highly dependent upon hormonal regulation; and (iii) the enzyme also catalyzes the steroid 17-20 lyase reaction, leading to the major androgens in the testis. As a prerequisite to the study of its regulation in intact cell, 17 alpha-hydroxylase was purified from calf testis microsomal preparations. Following five chromatographic steps, the enzyme was obtained as an apparently homogeneous protein of Mr = 57 kDa upon gel electrophoresis. The procedure yielded a recovery of about 10% as judged by cytochrome P-450 assay. Whereas 17 alpha-hydroxylase specific activity was about 30-fold enriched during the purification, that of the C17-20 lyase was increased by about 6-fold, strongly suggesting that its organelle environment may modulate the enzymatic activity. The purified enzyme yielded a 20 N-terminal amino-acid sequence showing a complete homology with that of its adrenal counterpart and a polyclonal antibody raised against our preparation revealed a 57 kDa protein band in bovine adrenocortical microsomal extracts, upon immunoblotting experiments. It was thus concluded that bovine 17 alpha-hydroxylase activity is supported by highly similar if not identical enzymatic proteins in both testis and adrenal cortex tissues. The purified P-450(17 alpha) preparation is now being used in reconstitution experiments which suggest that microsomal components may contribute to a different expression of the enzyme specificity in its native testis or adrenocortical intracellular environment, respectively.
J Steroid Biochem Mol Biol 1991
PMID:Purification and properties of steroid 17 alpha-hydroxylase from calf testis. 195 44

Testis, adrenal, ovary and placenta contain a microsomal cytochrome P-450 that is capable of converting progesterone to androstenedione and pregnenolone to dehydroepiandrosterone. This conversion requires 17 alpha-hydroxylation followed by C17,20-lyase activity which are both catalyzed by this one protein. Gene cloning and Northern blotting reveal that, at least in man, the same gene is responsible for both testicular and adrenal enzymes. The enzyme was first purified from neonatal pig testis. Both the testicular and adrenal enzymes show a marked preference for the 5-ene substrate (pregnenolone) in keeping with the extensive use of the 5-ene pathway in that species. Affinity alkylation with 17 alpha-bromoacetoxyprogesterone reveals a conserved cysteine at the active site of the enzyme and confirms the conclusion that a single enzyme catalyzes both reactions. Under some circumstances the enzyme catalyzes only 17 alpha-hydroxylation to permit the formation of the C21 steroid cortisol. The regulation of lyase activity, i.e. the determination of the extent to which the second activity is expressed, results from the availability of P-450 reductase. No doubt the greater concentration of this protein in testicular as opposed to adrenal microsomes (x 3.5) is responsible for the production of androgens in the testis and cortisol in the adrenal. Testicular cytochrome b5 also specifically stimulates lyase activity and also causes the porcine enzyme to catalyze a new reaction, i.e. delta 16-synthetase, resulting in synthesis of the important pheromone androsta-4,16-dien-3-one from progesterone.
J Steroid Biochem Mol Biol 1991
PMID:Cytochrome P-450 C21scc: one enzyme with two actions: hydroxylase and lyase. 195 54

The cytochrome P-450 monooxygenase enzymes, NADPH-reductase and form 2, were demonstrated immunohistochemically in hamster tracheal epithelium that was regenerating after mechanical injury. Bromodeoxyuridine (BrdU), a thymidine analogue, was used to map the location and extent of the wound sites between 8 and 144 h post-injury. In the control and non-wounded areas of the epithelium, the secretory cells were labelled for the monooxygenase enzymes. Label was heaviest in the apical cytoplasm of these columnar cells. At 8 h, secretory cells at the wound margins migrated to cover the wound sites, becoming progressively flattened. Reaction product for monooxygenase enzymes was strong in these flat cells but immunolabelling for BrdU was very low. At 24 h many cells at the wound sites were labelled for BrdU (indicative of a high rate of cell division). Some cells were labelled for monooxygenase but many were not stained at this time. At 48 and 72 h post-injury, none of the cells within the wound sites (regenerating epithelium) were stained. Immunochemical labelling for the monooxygenase enzymes was restored to the nascent secretory cells as they differentiated in the wound sites, beginning at 96 h post-injury. Labelling was stronger at 120 and 144 h post-injury, comparable to that in the control epithelium. The observations suggest that the monooxygenase enzymes were retained by the secretory cells in the wound sites before they divided but were lost from their progeny. Then, the temporal sequence of monooxygenase expression was similar to the pattern of differentiation of nascent secretory cells during fetal development of the tracheal epithelium.
Virchows Arch B Cell Pathol Incl Mol Pathol 1990
PMID:Immunohistochemical demonstration of cytochrome P-450 monooxygenase in regenerating tracheal epithelium: a recapitulation of fetal development. 198 Jan 74

The nonciliated bronchiolar epithelial (Clara) cell of the mouse is highly susceptible to toxicants that undergo metabolic activation, presumably because this cell type has high levels of cytochrome P-450 monooxygenases. As a first step in further defining the role of Clara cells in pulmonary xenobiotic activation and detoxication, we have isolated Clara cells (75 to 80% purity) and characterized them morphologically and biochemically. The identity of Clara cells, confirmed by transmission electron microscopy, was based on several features, including abundant agranular endoplasmic reticulum, large mitochondria, and dense secretory granules. Immunocytochemistry of isolated mouse cells showed that the majority were positive with antibodies against three major components of the pulmonary cytochrome P-450 monooxygenase system, cytochrome P-450 isozymes 2 (IIB), 5 (IVB), and NADPH cytochrome P-450 reductase, purified from rabbit lung. The isolated cells also showed a positive reaction with an antibody against the cytochrome P-450 isozyme that is active in the stereoselective metabolism of naphthalene, cytochrome P-450 mN (mN). Immunocytochemistry using the antibody against cytochrome P-450 isozyme 6 (IA1), purified from rabbit lung, showed no reaction in the isolated cells. The presence of intact cytochrome P-450 protein was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blots of homogenates of isolated cell preparations. The N-demethylation of benzphetamine and epoxidation of naphthalene occurred at easily measurable rates in incubations of isolated Clara cells. In contrast, diols, quinones, and monohydroxylated benzo(a)pyrene metabolites, analyzed by high performance liquid chromatography, were undetectable in extracts of Clara cells incubated with 3H-labeled substrate.(ABSTRACT TRUNCATED AT 250 WORDS)
Am J Respir Cell Mol Biol 1991 Feb
PMID:Characterization of the cytochrome P-450 monooxygenase system in nonciliated bronchiolar epithelial (Clara) cells isolated from mouse lung. 199 Oct 74

The activity of the enzyme (16-ene-C19-steroid synthesizing enzyme) responsible for the conversion of C21-steroids to 16-ene-C19-steroids, which was localized on pig testicular microsomes, was inhibited by some typical imidazole antifungal compounds such as clotrimazole, econazole, miconazole and ketoconazole which are known to be universal inhibitors of cytochrome P-450-dependent enzymes. The 50% inhibitory concentrations of clotrimazole, econazole and miconazole were 0.29, 0.36 and 1.25 microM, respectively for 16-ene-C19-steroid synthesizing enzyme activity. Clotrimazole was the most powerful inhibitor of all the compounds examined, which shows the competitive inhibition for 16-ene-C19-steroid synthesizing enzyme activity. The Ki-value was 0.26 microM for its activity. The degree of the inhibition by these imidazole compounds was very similar to the inhibition of 17 alpha-hydroxylase and C17,20-lyase activities on pig testicular microsomes.
J Steroid Biochem Mol Biol 1991 Jan
PMID:Inhibitory effect of some imidazole antifungal compounds on the synthesis of 16-ene-C19-steroid catalyzed by pig testicular microsomes. 199 27


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