Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It has been previously shown that H2O2 inhibits lens 86Rb influx and results in modification of Na+,K+-ATPase with respect to ATP hydrolysis. The effect of H2O2 on ATP hydrolysis was further investigated using [gamma-32P]-ATP to examine the Na+,K+-ATPase phosphorylated intermediate. A Na+-dependent phosphorylated polypeptide with an apparent molecular weight of approximately 100 000 was detected in all lens preparations, irrespective of H2O2 treatment. Similar results were observed for partially purified Na+,K+-ATPase from bovine kidney, porcine brain and canine kidney.
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PMID:Phosphorylation of H2O2-treated lens Na+,K+-ATPase. 609 27

Asialoorosomucoid was conjugated to lactoperoxidase and bound specifically to the asialoglycoprotein receptor on the human cell line Hep G2 at 4 degrees C. The bound conjugates incorporated 125I into cell surface proteins in the presence of H2O2. When Hep G2 cells were allowed to endocytose the prebound conjugates by warming to 37 degrees C for 10 min or were incubated for 1 h at 23 degrees C in the presence of conjugate, addition of 125I and H2O2 at 4 degrees C now resulted in labelling of endocytic vesicle proteins. The cell surface labelling pattern and the endosome labelling pattern were compared and found to be distinct. A major component labelled by the endocytosed asialoorosomucoid conjugate is shown to be the transferrin receptor. This protein and a component of 230 000 daltons are enriched in the endosome relative to the cell surface. The endocytosed lactoperoxidase conjugate was also visualised at the morphological level. Characteristic endosome tubules and vesicles contained electron-dense peroxidase reaction product as did cell surface coated pits. Selective capture of some cell surface proteins but not others by coated pits presumably gives rise to the distinct polypeptide composition of the endosome.
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PMID:In situ 125I-labelling of endosome proteins with lactoperoxidase conjugates. 614 19

The myeloperoxidases possessing the specific activity of 500 000-700 000 of o-dianisidine units per 1 mg of protein were isolated and purified from the lysosome-like granules of pig and cattle neutrophylic leukocytes. The absorbance spectra for the enzymes in the visible region are identical; their molecular weight is 140 000-160 000. The enzymes are made up of two subunits, each containing a heavy (m. w. 68 000) and a light (m. w. 10 000) polypeptide chains. The pH optimum for myeloperoxidase oxidation of o-dianisidine lies around 5.8-6.2 for both enzymes. The dependence of the reaction rate on H2O2 concentration does not obey the Michaelis--Menten kinetics. The optimal concentrations of the reaction substrates are 0.34 mM for o-dianisidine and 0.075 mM for H2O2. The amino acid composition and the peptide maps for pig and cattle myeloperoxidases are in many ways similar, showing no coincidence of enzymes, however, in terms of antigenic determinants. The similarities of some physico-chemical properties of pig and cattle enzymes and their immunological differences are discussed.
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PMID:[Comparison of various physico-chemical properties of pig and cattle myeloperoxidases]. 627 78

The yeast Saccharomyces cerevisiae, produces a cytochrome P-450 enzyme with a Soret peak in the reduced-CO difference spectrum at 448 nm. The enzyme purified to homogeneity (88-97% pure on a specific content basis) has a molecular wt. of 55 500 as determined by SDS-PAGE. Amino acid analysis of yeast cytochrome P-448 revealed 407 amino acid residues per molecule with a 43% complement of hydrophobic residues. Although the number of residues is smaller than cytochrome P-448 enzymes from mammalian sources, the percentage of hydrophobic residues is almost identical. Estimation of the haem content of yeast cytochrome P-448 showed that one haem group was present per molecule. Phospholipid was present at very low levels. The molecular wt. of the polypeptide chain plus an estimated 5-6 units of hexose and of hexosamine is in good agreement with the molecular wt. value obtained from SDS-PAGE. A reconstituted system of purified cytochrome P-448, purified NADPH-cytochrome P-450 (c) reductase and phospholipid showed aryl hydrocarbon hydroxylase activity towards benzo[a]pyrene. Both protein components, NADPH and dilauroyl phosphatidylcholine (or emulgen 911) were necessary for full activity. The NADPH requirement could be replaced by cumene hydroperoxide or H2O2 generated in situ from a glucose oxidase system; in each case Vmax is increased, but the apparent affinity for benzo[a]pyrene, as measured by an increased Km, is lowered. The spin state of purified yeast cytochrome P-448 was 94% low spin (22 degrees C) as determined from the temperature-dependent spin-state equilibrium. The addition of benzo[a]pyrene to this enzyme resulted in a change to higher spin state (18% high spin at 22 degrees C). Equilibrium gel filtration analysis of the number of benzo[a]pyrene binding sites per mole of enzyme monomer showed a value of 1 for purified yeast cytochrome P-448 and 6 for this enzyme in microsomal form. The corresponding values for purified and microsomal cytochrome P-450 from phenobarbital-pretreated rats are 1 and 6, respectively. However, purified cytochrome P-448 from beta-naphthoflavone-induced rats gave a value of 6 benzo[a]pyrene binding sites. Type I binding spectra with purified yeast cytochrome P-448 were observed with benzo[a]pyrene, lanosterol, ethylmorphine, dimethylnitrosamine, sodium phenobarbitone and perhydrofluorene. Type II spectral changes were observed with imidazole, aniline and benzphetamine. Cytochrome P-448 from Saccharomyces cerevisiae is identified as a distinct enzyme of the P-450 family. This enzyme however has many properties in common with cytochrome P-448 from mammalian sources.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Studies on the properties of highly purified cytochrome P-448 and its dependent activity benzo[a]pyrene hydroxylase, from Saccharomyces cerevisiae. 632 93

Soluble proteins from the human lens nucleus were incubated for 12 weeks with 0, 10, 100 and 1000 microM-H2O2. Treatments were monitored for alterations in cysteine (sulphydryl), methionine, tryptophan and other amino acids; protein size, solubility and conformation; polypeptide sizes; and non-tryptophan fluorescence. Progressive changes were observed in several of these parameters. Cysteine (up to 100%) and methionine (up to 45%) were rapidly oxidized but no significant alterations were found in any other amino acids. No new chromophores were generated but the non-tryptophan fluorescence was enhanced three-fold. The gradually increasing solvent accessibility of tryptophan residues indicated that the proteins were undergoing conformational alterations. This was accompanied by the insolubilization of protein (up to 75%). The insoluble proteins consisted largely of covalently cross-linked polymers of the lens polypeptides. Disulphide bonds and dityrosine were shown not to be involved in the cross-linking. The modifications observed, as well as their order and extent, are very similar to those found in the cataractous lens. Our observations suggest that low concentrations of H2O2 may be responsible for the oxidative modification of lens proteins during the development of senile nuclear cataracts.
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PMID:The effects of hydrogen peroxide on lens proteins: a possible model for nuclear cataract. 670 43

In contrast to other tissues, the lens exists in a milieu containing relatively high (micromolar) concentrations of H2O2. It has been demonstrated that activation of H2O2 to more-potent oxidant species via the heme-undecapeptide from cytochrome c produces alterations in lens crystallin polypeptides similar to the changes found in cataract. These include crystallin polypeptide crosslinking and the development of a blue fluorescence not attributable to tryptophan. Of the three classes of mammalian crystallins, gamma-crystallin is crosslinked by heme peptide-H2O2, whereas alpha and beta are not. Heme peptide plus H2O2 generates dityrosine from free tyrosine, and, concomitant with crosslinking, the gamma-crystallin exposed to this system develops a new fluorophor with the the characteristics of dityrosine. The findings with bovine and human crystallins are identical in this regard. In addition to the oxidation of tyrosine, exposure to heme peptide-H2O2 results in the oxidation of tryptophan. The intrinsic fluorescence of alpha, beta, and gamma-crystallins is due primarily to tryptophan, and the intrinsic fluorescence of each is decreased by heme peptide-H2O2. Thus, tryptophan oxidation occurs in all crystallins, but crosslinking occurs only in gamma-crystallin and is associated with oxidation of tyrosine.
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PMID:An analysis of the H2O2-mediated crosslinking of lens crystallins catalyzed by the heme-undecapeptide from cytochrome c. 673 43

Generation of hydrogen peroxide in adipocyte plasma membrane and its intracellular metabolism and regulatory role have been shown by Mukherjee and co-workers to be a major effector system for insulin [Fedn Proc. 35, 1694 (1976); Archs Biochem. Biophys. 184, 69 (1977); Biochem. Pharmac. 27, 2589 (1978); Fedn Proc. 37, 1689 (1978); and Biochem. Pharmac. 29, 1239 (1980)]. The possible involvement of this mechanism in the action of structurally similar polypeptides having some insulin-like metabolic effects was investigated. The beta-subunit of nerve growth factor (2.5 S NGF, mol. wt 13,500) which has a striking structural homology with proinsulin and has been reported to exert certain insulin-like metabolic effects in its own target tissues (e.g. growing neurites and sympathetic ganglia), and the insulin-derived polypeptides, desalanine-insulin and desoctapeptide-insulin, as well as proinsulin, were examined for their effects on rat adipocytes, employing the technique of formate oxidation. Both NGF and proinsulin caused increased [14C]formate oxidation, showing similar intrinsic activities, up to a maximum of 140-160% of the basal rate; insulin increased the rate to 190-210% of the basal rate. The relative potencies of the hormones toward H2O2 formation and stimulation of the pentose phosphate pathway activity were: insulin (EC50: 2.5 x 10(-11) M), desalanine-insulin (EC50: 2.5 x 10(-10) M), proinsulin (EC50: 8 x 10(-9) M), and NGF (EC50: 10(-9) M). The biologically inactive derivative, desoctapeptide-insulin, did not stimulate glucose oxidation, although it caused a small increase in formate oxidation, with an EC50 of 5 x 10(-7) M, indicating a suboptimal level of H2O2 formation in the elevation of the hexose monophosphate shunt activity. 3-Amino-1,2,4-triazole (50 mM), which irreversibly decomposes the peroxidatic compound II of the catalase: H2O2 complex, inhibited formate oxidation to a greater extent in the hormone-treated cells than in the control cells, whereas sodium azide, an inhibitor of the hemoprotein, catalase, completely inhibited it. The abilities of the polypeptides to stimulate H2O2 formation correlated with their abilities to promote lipogenesis from [U-14C]-D-glucose, as expected of insulin. The cellular GSH/GSSG ratio increased concomitantly with the stimulation of glucose oxidation via the shunt, indicating a tight coupling between these processes. The results confirm that the hydrogen peroxide production is a common basis of the metabolic actions of growth-promoting polypeptide hormones or mitogens beyond their respective receptors.
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PMID:Similar activities of nerve growth factor and its homologue proinsulin in intracellular hydrogen peroxide production and metabolism in adipocytes. Transmembrane signalling relative to insulin-mimicking cellular effects. 715 Mar 45

A protein has been solubilized and purified to homogeneity from the microsomal fraction of goat submaxillary gland. This protein can preferentially be iodinated to form triidothyronine and thyroxine with the help of submaxillary peroxidase (donor:hydrogen-peroxide oxidoreductase, EC 1.11.1.7) solubilized and purified from the same microsomal fraction. The protein can also be isolated from soluble supernatant and was found to be identical to the microsomal protein as judged by their moelcular properties as well as the formation of triiodothyronine and thyroxine. The protein has the molecular weight of 120 000 and contains two unequal subunits of molecular weight of 80 000 and 44 000. The molecular weight of the peroxidase is 72 000 and consists of a single polypeptide chain. The enzyme has the Rz value of 0.4 and is inhibited by azide and cyanide. Mersalyl, a mercurial, strongly inhibits the enzyme activity while N-ethylmaleimide cannot. The enzyme can catalyze the formation of 62 mumol of I3-/min per mg of protein at its optimun pH of 5.2. The apparent Km for H2O2 and KI is 0.16 . 10(-3) M and 1 . 10(-3) M, respectively.
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PMID:Studies on peroxidase-catalysed formation of thyroid hormones on a protein isolated from submaxillary gland. 736 31

The subunit composition of fully reduced bovine thyroglobulin consists of two polypeptide chains with molecular weights near 300,000. These two chains have been separated on sodium dodecyl sulfate gels by electrophoresis and were referred to as S and F. The effect of incubating native bovine thyroglobulin with a commercial preparation of horseradish peroxidase resulted in the conversion of S to F (and faster migrating polypeptides). Since this reaction was independent of the presence of H2O2 and iodide, it was necessary to demonstrate that the activity was present in the peroxidase enzyme which could be identified by its heme group. When the enzyme preparation was fractionated on Sephadex G-100, the activity responsible for the conversion of S to F was not associated with the heme peak but with another protein peak which eluted later on the column. Proteolytic inhibitors, such as phenylmethyl sulfonyl fluoride and pancreatic trypsin inhibitor, caused partial inhibition of the activity responsible for the conversion of S to F, whereas inhibitors of peroxidase activity had no effect. Guinea pig thyroglobulin was less susceptible to the proteolytic activity present in the peroxidase preparation than bovine thyroglobulin. The subunit composition of guinea pig thyroglobulin is different from that of bovine, since three bands of different sizes are present. The 300,000 mol wt subunit of guinea pig thyroglobulin (band A) ws largely degraded, whereas the 210,000 mol wt subunit (band B) was partially degraded and the 100,000 mol wt subunit (band C) was unaffected.
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PMID:Enzymatic conversion of the major polypeptide chains of thyroglobulin. 747 69

The cDNA encoding Mn peroxidase isozyme H4 from Phanerochaete chrysosporium was expressed in Escherichia coli. The portion of the cDNA encoding the enzyme's signal peptide, not found in the processed holoenzyme, was deleted from the cDNA. The polypeptide was produced as inactive inclusion bodies that could be solubilized in 8 M urea and the reducing agent dithiothreitol. Reconstitution of activity was accomplished by diluting the urea concentration to 2M in the presence of hemin, calcium, and oxidized glutathione. All of the additives were required for recovery of activity. The activity of the recombinant enzyme was dependent on both Mn2+ and H2O2.
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PMID:Expression of fungal Mn peroxidase in E. coli and refolding to yield active enzyme. 748 73


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