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)

Two photoproducts, derived from UV-irradiation of the amino acid L-tryptophan and with high Ah (TCDD) receptor binding affinity, were tested for genotoxic and antimutagenic effects. The two indolo[3,2-b]carbazole derivatives, with the molecular weights of 284 and 312, respectively, were tested in Saccharomyces cerevisiae strain D7 for mitotic gene conversion and reverse mutation and in strain RS112 for sister chromatid conversion and gene conversion. No significant (P > 0.05) genotoxic effects were found in strain D7, while strain RS112 showed a small but significant increase in the frequency of sister chromatid conversions. In Chinese hamster ovary (CHO) cells the two compounds induced a statistically significant but less than twofold increase in the frequency of sister chromatid exchanges (SCE). No mutations were detected when the compounds were tested in Salmonella typhimurium strains TA98 and TA100. However, both 284 and 312 acted as antimutagens on strain TA100 + S9 in the presence of benzo(a)pyrene. The decrease in mutagenicity by the most potent compound 284 was 20 revertants/nmol. This effect could be explained by an inhibitory effect on the cytochrome P450-dependent ethoxyresorufin O-deethylase (EROD) activity as seen in rat hepatocytes. The two compounds were also tested with hamster cells expressing rat cytochrome P-450IA1. The results support the conclusion that this cytochrome P-450 isozyme is inhibited by the tryptophan photoproducts. Similar results were also seen with two other high affinity Ah receptor ligands the quinazolinocarboline alkaloids rutaecarpine and dehydrorutaecarpine.
Environ Mol Mutagen 1992
PMID:Certain tryptophan photoproducts are inhibitors of cytochrome P450-dependent mutagenicity. 133 May 48

An octa-heme cytochrome c3, isolated as a dimeric molecule of about 30 kDa from the anaerobic bacteria Desulfovibro desulfuricans Norway, has been crystallized in a form suitable for atomic resolution X-ray structural investigations. The crystals are trigonal, space group P3(1)21 (or its enantiomorph P3(2)21), with cell dimensions: a = b = 72.9 A c = 62.7 A. The asymmetric unit contains most probably one monomer and a solvent content of about 60%. Under this assumption, the crystallographic 2-fold axis relates the two subunits of the dimer. Diffraction extends to 2.0 A.
J Mol Biol 1992 Dec 05
PMID:Crystallization and preliminary crystallographic study of an octa-heme cytochrome c3 from Desulfovibrio desulfuricans Norway. 133 87

We have compared kinetoplast DNA maxicircles of tunicamycin- and arsenite-resistant variants of repeatedly cloned Leishmania mexicana amazonensis showing DNA amplification with wild-type and arsenite-resistant variants of the same lineage that do not show DNA amplification. DNA restriction patterns and the degree of cross-hybridization between maxicircle DNA fragments of parasites displaying DNA amplification and those of parasites without amplification were examined. In addition, the nucleotide sequence of the cytochrome b (Cyb) gene from the coding region was compared between these two groups of parasites. Extensive changes were found in the nucleotide sequences and the amino acid sequences of the cytochrome gene of the maxicircles of variants with DNA amplification. The Cyb genes from both groups had much shorter open reading frames than the same gene from Leishmania tarentolae and Trypanosoma brucei. The simultaneous changes in maxicircles and minicircles of these variants suggest that they may confer the advantage of maintaining viable mitochondrial function under selective pressure.
Mol Biochem Parasitol 1992 Dec
PMID:Characterization of sequence changes in kinetoplast DNA maxicircles of drug-resistant Leishmania. 133 69

Xenobiotic transformation by Streptomyces griseus (ATCC13273) is catalysed by a cytochrome P-450, designated cytochrome P-450soy. A DNA segment carrying the structural gene encoding P-450soy (soyC) was cloned using an oligonucleotide probe constructed from the protein sequence of a tryptic peptide. Following DNA sequencing the deduced amino acid sequence of P-450soy was compared with that for P-450cam, revealing conservation of important structural components including the haem pocket. Expression of the cloned soyC gene product was demonstrated in Streptomyces lividans by reduced CO:difference spectral analysis and Western blotting. Downstream of soyC, a gene encoding a putative [3Fe-4S] ferredoxin (soyB), named ferredoxinsoy, was identified.
Mol Microbiol 1992 Aug
PMID:Cloning, nucleotide sequence determination and expression of the genes encoding cytochrome P-450soy (soyC) and ferredoxinsoy (soyB) from Streptomyces griseus. 848 14

The regulation of steroidogenesis by luteinizing hormone (LH) was studied in granulosa cells during follicular development using a fluorescent reporter assay based on the metabolism of a fluorescent probe specific for cytochrome P-450SCC (cholesterol side-chain cleavage enzyme). Intact granulosa cells or mitochondria were obtained from the first (F1) second (F2) and third (F3) largest preovulatory follicles of the hen ovary and incubated with the fluorogenic substrate. Metabolism of this substrate by cytochrome P-450SCC generates the highly fluorescent resorufin anion (the fluorescent reporter). In both mitochondria and intact granulosa cells, incubated with the fluorescent substrate, an increase in resorufin fluorescence was observed and the increase was greater in samples derived from F1 than in samples from F2 or F3. In cells, LH added simultaneously with the P-450SCC substrate significantly increased resorufin fluorescence above control values in a time- and dose-dependent manner up to 2-3 h after the incubation was initiated. Forskolin and 8-bromo-cAMP also stimulated metabolism of the P-450SCC substrate significantly by 15 min. When granulosa cells were preincubated with LH before exposure to the P-450SCC substrate resorufin fluorescence was significantly attenuated compared to controls (not exposed to LH in the preincubation period). The decrease in resorufin fluorescence observed when cells were pretreated with LH, may be due to the release of cholesterol from endogenous pools and its competition with the exogenous fluorogenic for the substrate P-450SCC enzyme. In granulosa cells that were preloaded with the P-450SCC substrate, the stimulatory effect of LH treatment remained constant from 30 min to 2 h after hormone addition. The results show that this fluorescent probe can be used in a rapid assay for the continuous measurement of the acute effects of hormone agonists on cholesterol conversion to pregnenolone in steroidogenic cells.
J Steroid Biochem Mol Biol 1992 Nov
PMID:Hormone stimulated steroid biosynthesis in granulosa cells studied with a fluorogenic probe for cytochrome P-450SCC. 141 83

The genes encoding the photosynthetic cytochrome b6 (petB) and subunit 4 (petD) have been cloned and sequenced from the unicellular, photoheterotrophic, transformable cyanobacterium Synechococcus sp. PCC 7002, formerly designated Agmenellum quadruplicatum. The gene arrangement was found to be similar to that reported in the cyanobacterium Nostoc PCC 7906. The DNA and derived protein sequences were compared to chloroplast and the other cyanobacterial sequences. By pulsed-field electrophoresis, the petBD operon and the petCA operon, encoding the Rieske iron-sulfur protein and cytochrome f, were found to be located on separate, unlinked, Not I-digested DNA fragments. The petBD operon was found on the third largest Not I fragment (NC-325) while the petCA operon was found on the second largest Not I fragment (NB-370). These results suggest the two operons are not in proximity. The 1.35 kb transcript was shown to be light-regulated. Transcripts from cells grown under constant illumination showed a decrease in petB transcript levels to undetectable levels within 2 h after the cells were placed in the dark. Upon reillumination, transcript levels rose to three-fold over that seen initially under constant illumination.
Plant Mol Biol 1992 Nov
PMID:Cloning and sequencing of the petBD operon from the cyanobacterium Synechococcus sp. PCC 7002. 142 Nov 51

Hydrostatic pressure has been used to convert cytochrome P-450camphor to cytochrome P-420. The latter is an inactivated but soluble and undenaturated form of cytochrome P-450camphor. Using camphor analogues as probes of the active site we show that the inactivation volume change is directly correlated to the initial degree of hydration of the heme pocket. The values range between -73 ml/mol and -197 ml/mol [Di Primo, C., Hui Bon Hoa, G., Douzou, P. & Sligar, S. G. (1990) Eur. J. Biochem. 193, 383-386] for a totally hydrated (substrate-free, low-spin, six coordinated heme iron) and a non-hydrated (camphor-bound, high-spin, five coordinated heme iron) heme pocket. These results suggest that the larger value, -197 ml/mol, for the inactivation volume change is due to a hydration change of the heme pocket resulting from the displacement of the substrate during the compression and the subsequent entrance of water molecules. Similarly, the stability of the protein against compression is correlated with water accessibility to the active site. Increase in substrate mobility by loss of specific interactions with both regions of well defined secondary structure of cytochrome P-450camphor results in an increase of water accessibility and decrease of stability. Thus for camphor and adamantanone which strongly interact with the protein and exclude water from the active site [Poulos, T. L., Finzel, B. C. & Howard, A. J. (1987) J. Mol. Biol. 195, 687-700; Raag, R. & Poulos, T. L. (1989) Biochemistry 28, 917-922] the increase in stability compared to the free protein is roughly 30 kJ/mol at 20 degrees C. With smaller substrates such as norcamphor, which loosely fits into the active site and does not completely exclude water [Raag, R. & Poulos, T. L. (1989) Biochemistry 28, 917-922], the increase in stability is only 7 kJ/mol. Finally these results suggest that cytochrome P-420 induced by hydrostatic pressure is a unique form where the active site is hydrated and camphor is displaced from its binding site.
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PMID:Heme-pocket-hydration change during the inactivation of cytochrome P-450camphor by hydrostatic pressure. 142 65

Several functional domains, especially the active site regions, in aromatase cytochrome P450 were inferred by alignment of amino acid sequences of the enzyme from five species, human, rat, mouse, chicken, and trout, and that of Pseudomonas putida cytochrome P450cam, whose x-ray structure has been determined (Poulos, T.L., Finzel, B.C., and Howard, A.J. (1987) J. Mol. Biol. 195, 687-700). The predicted functions of these domains have been evaluated by site-directed mutagenesis. Eighteen mutants, including seven new mutants, have been generated in this laboratory. The seven newly prepared mutants are Q123E, Q123H, T310S, T310C, R365K, R365A, and N delta 20 (a mutant without the first 20 amino acids). The preparation and characterization of these new mutants are described. The structural model described in this paper should be very useful for future structure-function studies of aromatase by site-directed mutagenesis.
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PMID:Functional domains of aromatase cytochrome P450 inferred from comparative analyses of amino acid sequences and substantiated by site-directed mutagenesis experiments. 828 24

Antidepressant drugs that contain alkylaminoalkyl substituents have been associated with serious pharmacokinetic interactions in humans that may be related to the inhibition of cytochrome P450 (P450) enzymes. In this study, the propensity of the tricyclic antidepressant nortriptyline (NOR) to inhibit individual microsomal P450 enzymes in rat liver was investigated to provide a mechanistic explanation for these pharmacokinetic interactions. Enzyme kinetic studies revealed that NOR inhibited steroid 2 alpha-, 6 beta, 7 alpha-, and 16 alpha-hydroxylation in untreated rat liver with Km/Ki ratios of 0.53, 0.59, 0.25, and 0.29, respectively. When the drug was preincubated with microsomes and NADPH before testosterone hydroxylation was conducted, marked increases in the Km/Ki ratios were observed (to 8.8, 3.9, 0.62, and 13, respectively). Thus, enzymic oxidation of NOR enhanced its inhibition capacity against P450 activities. Indeed, the altered Km/Ki ratios indicate 17-, 6.6-, 2.5-, and 47-fold increases in inhibition of the four pathways of testosterone hydroxylation after the biotransformation of NOR to its metabolites. From these experiments it was apparent that testosterone 2 alpha- and 16 alpha-hydroxylations, catalyzed predominantly by P450 2C11, were subject to the most pronounced increase in inhibition. Under these conditions, the apparent content of microsomal P450 was decreased, thus suggesting the formation of a NOR metabolite intermediate (MI) complex with the cytochrome. Further, optical difference spectroscopy of NADPH-supported metabolism of NOR in microsomes and in a reconstituted system incorporating purified P450 2C11 indicated the appearance of an absorbance peak near 454 nm, similar to those produced by triacetyloleandomycin, SKF 525-A, and orphenadrine. Formation of this absorbance peak in microsomes was inhibited by an antibody raised against the male-specific P450 2C11. Because oxidative metabolism of NOR to inhibitory products would not necessarily involve MI complexation, additional experiments were undertaken in which NOR-related free metabolites produced in microsomal incubations were removed on Sep-Pak mini-C18 columns before estimation of testosterone hydroxylation. The principal finding from this experiment was that P450 3A2-dependent steroid 6 beta-hydroxylase activity was inhibited to a much lesser extent after removal of unbound NOR metabolites on Sep-Pak columns (25% inhibition after Sep-Pak extraction, compared with 82% inhibition observed when all NOR metabolites were present during subsequent testosterone hydroxylation); inhibition of P450 2C11-mediated 2 alpha- and 16 alpha-hydroxylation was not noticeably different after Sep-Pak treatment.(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Pharmacol 1992 Nov
PMID:Metabolite intermediate complexation of microsomal cytochrome P450 2C11 in male rat liver by nortriptyline. 143 57

We present an analysis of several molecular dynamics trajectories of substrate-bound cytochrome P450cam. Trajectories were calculated for the native substrate, camphor, as well as for the alternative substrates, norcamphor and thiocamphor. The system modeled consisted of the crystallographically resolved amino acids, the heme group with a single oxygen atom as the distal ligand, the bound substrate, and the crystallographic waters. These trajectories of the presumptive ferryl oxygen intermediate were used to predict regiospecificity of hydroxylation and coupling between NADH consumption and product formation. Simple geometric criteria in combination with electronic considerations were used to calculate the probability of hydroxylation at specific sites on the substrate. We found that for all the cases examined, the predicted product ratios were in good agreement with the experimentally observed values. We also determined that these simple geometric criteria can be used to predict the degree of coupling between NADH consumption and product formation for a given substrate, which was in good agreement with the experimental values.
J Comput Aided Mol Des 1992 Oct
PMID:Predicting the product specificity and coupling of cytochrome P450cam. 147 94


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