Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A highly purified membrane preparation derived from the microsomal fraction of rat hepatocytes has been chemically characterized and fractionated by means of gel filtration. The preparation has been freed of ribosomes and intravesicular protein and has a composition on a w/w basis of 52.1% protein, 45.0% phospholipid, 2.9% carbohydrate and no RNA. 97 +/- 2% of the total membrane phosphorus is accounted for as phospholipid phosphorus. Determination of the molecular weight distribution of the constituent polypeptides by sodium dodecyl sulfate-polyacrylamide gel electrophoresis gave values ranging from 171 000 to 16 000 for the major classes of proteins. Although several membrane glycoproteins have been indentified, the most prominent species has an apparent molecular weight of 171 000, 40% of the total microsomal protein is present in the 49 000-60 000 molecular weight region. Examination of the intrinsic polypeptide composition of membranes obtained from smooth and degranulated rough endoplasmic reticulum revealed no detectable qualitative differences. Sodium dodecyl sulfate-solubilized microsomal membrane proteins were separated by gel filtration into much simplified molecular weight classes, some of which showed predominantly a single electrophoretic component. Amino acid analysis of individual fractions showed a noticeable trend toward a decreasing ratio of acidic to basic residues with decreasing molecular weight. Membrane phosphorus was distributed between two chromatographic fractions: one containing membrane phospholipid (97% of the total) as well as essentially all the cholesterol, the other, at the inclusion volume of the gel filtration system, containing small molecular weight species (3% of the total phosphorus). The absence of a ribonuclease-resistant RNA component eluting near the void volume clearly distinguishes the microsomal membrane from the nuclear envelope.
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PMID:Characterization of the membrane matrix derived from the microsomal fraction of rat hepatocytes. 127 22

The efficacy of Picroliv, a standardized iridoid glycoside fraction of Picrorhiza kurroa, was studied against the Amanita phalloides-induced biochemical changes in rat liver. A phalloides (50 mg.kg-1) caused significant increases in the activities of hepatic 5'-nucleotidase, gamma-glutamyl transpeptidase, acid ribonuclease, and succinate dehydrogenase, but a decrease in glucose-6-phosphatase. The level of cytochrome P-450 in microsomal fraction and content of glycogen in liver showed significant depletions. Picroliv (25 mg.kg-1.d-1 x 10 d) provided significant restorations of all the biochemical changes poisoned by A phalloides except cytochrome P-450 and glycogen. These results demonstrated the protective effect of Picroliv against A phalloides-induced hepatotoxicity in rats.
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PMID:Effects of picroliv, the active principle of Picrorhiza kurroa, on biochemical changes in rat liver poisoned by Amanita phalloides. 135 30

We have examined the tissue-specific expression and inducibility of acyl-CoA oxidase and cytochrome P450IVA1 (P450IVA1) RNA in rats. Groups of three rats were dosed daily by gavage with methylclofenapate at 25 mg/kg in 5 ml/kg corn oil for nine weeks, or were administered a vehicle control. P450IVA1 and acyl-CoA oxidase RNA were detected using an RNase protection assay. Similar levels of acyl-CoA oxidase RNA were present in control liver and kidney, but the level of this RNA in lung, muscle and testis was 6-11%, and in pancreas was 0.13%, of that in liver. Treatment of rats with methylclofenapate led to an 11-fold induction of acyl-CoA oxidase RNA in liver and also produced a significant induction of this RNA in kidney, lung, muscle and testis of 1.7-fold, 1.3-fold, 2-fold and 1.7-fold, respectively. Acyl-CoA oxidase RNA was not induced in pancreas. P450IVA1 RNA was present in control liver and also in kidney of control rats at 28% of the level in liver. In contrast to acyl-CoA oxidase RNA, P450IVA1 RNA was not detected in lung, pancreas or testis. Methylclofenapate treatment of rats led to an 18-fold induction of P450IVA1 RNA in liver, and a sevenfold induction in kidney. Induction of P450IVA1 was not detected in any of the other tissues examined. Quantification of the relative amounts of acyl-CoA oxidase and P450IVA1 RNA in control liver revealed that acyl-CoA oxidase RNA was present in a 17.5-fold molar excess over P450IVA1 RNA. Western blotting with an anti-P450IVA IgG revealed two bands of similar apparent molecular mass in liver and kidney microsomes, but not in microsomes from the testis of control rats. Methylclofenapate treatment of rats caused an increase in the intensity of these bands in microsomes from liver, but no induction was obvious in kidney. Immunocytochemical staining for both the microsomal P450IVA and peroxisomal acyl-CoA oxidase proteins was restricted to the proximal convoluted tubule in the kidney cortex, with staining being most intense in the S3 region.
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PMID:Differential tissue-specific expression and induction of cytochrome P450IVA1 and acyl-CoA oxidase. 137 90

The in vitro metabolism of [14C]toluene by liver microsomes and liver slices from male Fischer F344 rats and human subjects has been compared. Rat liver microsomes produced only benzyl alcohol from toluene. Liver microsomes from human subjects metabolized toluene to benzyl alcohol, benzaldehyde, and benzoic acid. Liver microsomes from one human donor also produced p-cresol and o-cresol. The overall rate of toluene metabolism by human liver microsomes was 9-fold greater than by rat liver microsomes. Human liver microsomal metabolism of benzyl alcohol to benzaldehyde required NADPH and was inhibited by carbon monoxide and high pH (pH 10). but was not inhibited by ADP-ribose or sodium azide. These results suggest that cytochrome P-450, rather than alcohol dehydrogenase, was responsible for the metabolism of benzyl alcohol to benzaldehyde. Human and rat liver slices metabolized toluene to hippuric acid and benzoic acid. The overall rate of toluene metabolism by human liver slices was 1.3-fold greater than by rat liver slices. Cresols and cresol conjugates were not detected in human or rat liver slice incubations. Covalent binding of [14C]toluene to human liver microsomes and slices was 21-fold and 4-fold greater than to the comparable rat liver preparations. Covalent binding did not occur in the absence of NADPH, was significantly decreased by coincubation with cysteine, glutathione, or superoxide dismutase, and was unaffected by coincubation with lysine. Protease and ribonuclease digestion decreased the amount of toluene covalently bound to human liver microsomes by 78% and 27% respectively. Acid washing of human liver microsomes had no effect on covalent binding.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolism and covalent binding of [14C]toluene by human and rat liver microsomal fractions and liver slices. 198 39

Two forms of plasminogen activators inhibitor 2 (PAI-2) are synthesized by human and murine monocytes/macrophages: one accumulates in the cytosol, while the other is translocated into the endoplasmic reticulum, glycosylated and secreted. We show here that a single mRNA encodes both forms of PAI-2. Firstly, a single PIA-2 mRNA was detected by Northern blot hybridization and by RNase protection. Secondly, transfection of a PAI-2 cDNA led to the synthesis of both forms of PAI-2. Finally, in vitro translation of an mRNA transcript of the PAI-2 cDNA in the presence of microsomal membranes generated two topologically distinct forms of PAI-2. The cytosolic and secreted forms of PAI-2 do not result from the use of two translation start sites, since their synthesis initiates at the same AUG, in a sequence context that is conserved between the human and murine genes. Thus, the accumulation of one polypeptide into two topologically distinct cellular compartments can be achieved by facultative translocation.
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PMID:Facultative polypeptide translocation allows a single mRNA to encode the secreted and cytosolic forms of plasminogen activators inhibitor 2. 258 99

Protein disulfide isomerase (PDI) is a multifunctional microsomal enzyme that participates in the formation of protein disulfide bonds. PDI catalyzes the reduction of protein disulfide bonds in the presence of excess reduced glutathione and has been implicated in the reductive degradation of insulin; E. coli thioredoxin is homologous to two regions in PDI and can also degrade insulin. PDI activity, measured by 125I-insulin degradation or reactivation of randomly oxidized RNase in the presence of reduced glutathione, is non-competitively inhibited by estrogens; half-maximal inhibition was observed at approximately 100 nM estrogen. Other steroid hormones at 1 microM had little or no effect. PDI segment 120-163 (which corresponds to exon 3 of the PDI gene) and 182-230 have significant similarity with estrogen receptor segments 350-392 and 304-349, respectively, located in the estrogen binding domain but not with the steroid domains of the progesterone and glucocorticoid receptors or with thioredoxin, which is insensitive to estrogens. We propose the hypothesis that enzymes can acquire sensitivity to a hormone via exon shuffling to the enzyme gene from the DNA region coding for the hormone binding domain of the hormone's receptor.
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PMID:Selective inhibition of protein disulfide isomerase by estrogens. 266 79

Protein disulfide-isomerase was isolated as a homogeneous protein from 15-day-old chick embryos. The enzyme has a molecular weight of 56,000 in SDS-polyacrylamide gel electrophoresis. Its Km value for randomly cross-linked ribonuclease, a protein used as a substrate for the enzyme, was 0.3 microM, and the Km value for DTT was 1.0 microM. Its optimum pH was 7.5 and its optimum temperature, 33 degrees C. The maximal velocity of pure protein disulfide-isomerase from chick embryos under optimal conditions was about 29,000 units/g. Protein disulfide-isomerase was able to activate purified prolyl 4-hydroxylase 2- to 3-fold, the activation being higher for enzyme stored for a longer time. This activation is probably due to the repairing of disulfide exchanges occurring in the prolyl 4-hydroxylase structure during purification and storage. Prolyl 4-hydroxylase activity was very stable in microsomes, however, and protein disulfide-isomerase was unable to increase the microsomal prolyl 4-hydroxylase activity, suggesting that prolyl 4-hydroxylase retains its native conformation in microsomes. Protein disulfide-isomerase was able to reactivate prolyl 4-hydroxylase inactivated by mild H2O2 treatment. The activity obtained after this treatment and protein disulfide-isomerase incubation corresponded to the amount of prolyl 4-hydroxylase tetramer found after H2O2 treatment. The data suggest that protein disulfide-isomerase is able to activate only the tetramer part of the enzyme preparation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Protein disulfide-isomerase retains procollagen prolyl 4-hydroxylase structure in its native conformation. 302 99

We have found that a soluble activity present in the postribosomal supernatant fraction of Saccharomyces cerevisiae stimulates posttranslational translocation of yeast prepro-alpha-factor across yeast microsomal membranes. Stimulation of translocation is not due to a nonspecific affect on ATP levels. The activity is likely to be due to protein(s) as it is destroyed by N-ethylmaleimide, protease, or heat treatment but not by incubation with RNase. Its apparent sedimentation coefficient is approximately 9.6 S.
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PMID:Protein translocation across the yeast microsomal membrane is stimulated by a soluble factor. 302 20

An inhibitor of microsomal dehydroepiandrosterone sulfatase was found in the soluble fraction of non-pregnant guinea pig liver. The extent of inhibitory effect was dependent on the concentration of soluble proteins. The inhibitor was partly purified by gel permeation and hydroxylapatite chromatography with a purification factor of 16.6. The soluble inhibitor was non-dialyzable, not destroyed by RNase or DNase digestion but totally destroyed by pronase digestion. The inhibitor is a soluble protein with a molecular weight of approximately 17,000 (determined by gel permeation chromatography). Inhibition of microsomal dehydroepiandrosterone sulfatase by the soluble inhibitor is a non-competitive inhibition. From this present finding the question arises whether the inhibitor could be involved in the regulation of the hydrolysis of dehydroepiandrosterone sulfate in the guinea pig liver.
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PMID:A dehydroepiandrosterone sulfatase inhibitory activity in soluble proteins of guinea pig liver. 303 97

Specific binding of steroid hormones to microsomes has been reported for several tissues. In the hen oviduct, this receptor appears to be very similar to activated cytosolic receptor. The microsomal receptor is readily solubilized, and resembles the cytosolic receptor in all physico-chemical characteristics: sedimentation coefficient approximately 4 S, Stokes radius 5.5 nm, slow dissociation rate of the complex, adsorption to polyanions. It is precipitated by an antibody to the cytosolic receptor. Microsomes display saturable binding of cytosolic receptor, with a Bmax of approximately 300 fmol/mg protein. This binding is also observed using microsomes from non-target tissues, and is decreased by treatment with RNase. It seems likely that microsomal binding is due to the high affinity of activated cytosolic receptor for RNA.
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PMID:Binding of activated progesterone receptor to microsomes. 389 1


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