Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0272170 (SDS)
 50,377 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Peroxidase (donor: H2O2 oxidoreductase [EC 1.11.1.7]) was purified from the culture broth of the hyphomycete Arthromyces ramosus in the early log phase to show a single band on SDS-PAGE. The crystals of A. ramosus peroxidase (ARP) were formed by salting out with ammonium sulfate at room temperature and pH 7.5. The repeated seeding technique was employed to grow the crystals to the size large enough for X-ray diffraction study. The crystals were characterized as tetragonal, space group P4(2)2(1)2, with unit cell dimensions of a = b = 74.5 A, c = 117.6 A. The asymmetric unit contains one molecule of peroxidase. They diffract X-rays to at least 2.0 A resolution and are stable to X-rays.
 ...
PMID:Crystallization and preliminary X-ray diffraction studies of peroxidase from a fungus Arthromyces ramosus. 838 20

A peroxidase was purified 98.3-fold from the culture filtrate of Pleurotus ostreatus with an overall yield of 12.4%. The molecular mass determined by gel filtration was found to be approx. 140 kDa. SDS-PAGE revealed that the enzyme consists of two identical subunits with a molecular mass of approx. 72 kDa. The pI value of this enzyme is approx. 4.3. The enzyme contains 41% carbohydrate by weight, and aspartic acid and asparagine (16.8%), and glutamic acid and glutamine (12.0%). The enzyme has the highest affinity toward synaptic acid and affinity towards various phenolic compounds containing methoxyl and p-hydroxyl groups, directly attached to the benzene ring. However, the enzyme does not react with veratryl alcohol and shows no affinity for nonphenolic compounds. The optimal reaction pH and temperature are 4.0 and 40 degrees C, respectively. The catalytic mechanism of the enzymic reaction is of the Ping-Pong type. The activity of the enzyme is competitively inhibited by high concentrations of H2O2 and its Ki value is 1.70 mM against H2O2. This enzyme contains approx. 1 mol of heme per mol of one subunit of the enzyme. The pyridine hemochrome spectrum of the enzyme indicates that the heme of P. ostreatus peroxidase is iron protoporphyrin IX. The EPR spectrum of the native peroxidase shows the presence of a high-spin ferric complex with g values at 6.102, 5.643 and 1.991.
 ...
PMID:Purification and characterisation of an extracellular peroxidase from white-rot fungus Pleurotus ostreatus. 838 25

Human term placental peroxidase [donor: hydrogen peroxide (H2O2) oxidoreductase] from non-smoking women was purified by extraction of the membrane fraction with 0.5 M Ca2+ followed by affinity chromatography on concanavalin A, hydrophobic chromatography on phenyl sepharose CL-4B and gel filtration chromatography on sephacryl S-200 columns. The final enzyme preparation was 110-fold pure when compared to the Ca2+ extract and the overall recovery of the procedure was 55 per cent. SDS-PAGE of the final product showed the presence of four protein staining bands of molecular weights 30, 32.5, 35 and 55 KDa. The purified peroxidase eluted as a single peak from the sephacryl S-200 column suggesting apparent homogeneity of the protein. The purified placental peroxidase oxidized thiobenzamide to its sulfoxide. The highest rate of TB S-oxidation under optimum conditions was 18 +/- 2.15 mumoles/min/mg protein. The H2O2-dependent thiobenzamide S-oxidation catalysed by the placental peroxidase was inhibited by KCN and NaN3 with IC50 values of 16.9 and 34 microM respectively.
 ...
PMID:Placental peroxidase--further purification of the enzyme and oxidation of thiobenzamide. 839 51

An oxalate oxidase (EC 1.2.3.4), which catalyzes aerobic oxidation of oxalate to CO2 and H2O2, has been purified to apparent homogeneity from 10-day-old leaves of grain sorghum hybrid CSH-5, as determined by disc-gel electrophoresis. The molecular weight of the enzyme was about 120,200 by Sephadex G-200 gel filtration, 62,000 by SDS disc-gel electrophoresis. The enzyme had an optimum pH of 5.0 and activation energy of 4.4 kcal/mol. The rate of reaction was linear up to 2 min. The Km value for oxalate was 0.78.10(-4) M. The enzyme was inhibited by EDTA, L-cysteine and sodium azide, but iodoacetate had no effect. The enzyme was strongly stimulated by Cu2+ and was unaffected by chloride ions in physiological concentration range. The better suitability of the enzyme for urinary oxalate determination is demonstrated.
 ...
PMID:Purification and properties of an oxalate oxidase from leaves of grain sorghum hybrid CSH-5. 842 16

We previously reported that rat glutathione transferase P-form (GST-P) is inactivated by hydrogen peroxide (H2O2). This involves formation of intra- or intersubunit disulfides, at least three extra bands with molecular masses of 21.5, 18, and 37 kDa being exhibited in addition to the native subunit band of 23.5 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under nonreducing conditions. In the present study, GST-P mutants whose cysteine residues were independently substituted with alanine (C14A, C47A, C101A, and C169A) by site-directed mutagenesis were used to identify the cysteine residues responsible for the disulfide bond formation. C14A and C169A were much more inactivated than native GST-P by 1 mM H2O2, whereas C47A and, especially, C101A appeared insensitive to H2O2. On SDS-PAGE, the 21.5-kDa band was not detected in either C47A or C101A. Hydrogen peroxide treatment of mouse GST II, highly homologous to rat GST-P but possessing glycine instead of cysteine at the 101st residue, did not result in generation of the 21.5-kDa band and was also associated with less inactivation. This band was therefore considered to be due to an intrasubunit disulfide bond between Cys-47 and Cys-101. The 37-kDa band was suggested to be due to the formation of intersubunit disulfide bonds between Cys-47 residues in different subunits. Thus the Cys-47 residue together with Cys-101 may be located in an important region for GSH binding, disulfide bond formation between these residues resulting in steric hindrance.
 ...
PMID:Identification of cysteine residues involved in disulfide formation in the inactivation of glutathione transferase P-form by hydrogen peroxide. 842 45

We have characterized a new selenium-dependent glutathione peroxidase, GSHPx-GI, by expressing a GSHPx-GI cDNA isolated from human hepatoma HepG2 cells in human mammary carcinoma MCF-7 cells, which have virtually undetectable expression of either the classical cellular enzyme, GSHPx-1, or GSHPx-GI at the protein level. One of the G418-resistant clones, neo-D1, expresses the transfected GSHPx-GI cDNA. This is based on 1) the presence of an additional GSHPx-GI DNA restriction fragment detected by Southern analysis; 2) the presence of a 1.9-kilobase (kb) GSHPx-GI mRNA in addition to the 1.0-kb endogenous mRNA by Northern analysis; and 3) the appearance of a 22-kDa 75Se-labeled protein which is absent in parental MCF-7 cells revealed by SDS-polyacrylamide gel electrophoresis. GSHPx-GI expressed in neo-D1 is a tetrameric protein localized in cytosol. GSHPx-GI does not cross-react with antisera against human GSHPx-1 or human plasma glutathione peroxidase (GSHPx-P). Similar substrate specificities are found for GSHPx-1 and GSHPx-GI; they both catalyze the reduction of H2O2, tert-butyl hydroperoxide, cumene hydroperoxide, and linoleic acid hydroperoxide with glutathione, but not of phosphatidylcholine hydroperoxide. GSHPx-GI mRNA was readily detected in human liver and colon, and occasionally in human breast samples, but not other human tissues including kidney, heart, lung, placenta, or uterus. In rodent tissues, GSHPx-GI mRNA is only detected in the gastrointestinal tract, and not in other tissues including liver. In fact, GSHPx-GI appears to be the major glutathione-dependent peroxidase activity in rodent GI tract. This finding suggests that GSHPx-GI could play a major role in protecting mammals from the toxicity of ingested lipid hydroperoxides. In conclusion, we have demonstrated that GSHPx-GI is the fourth member in the selenium-dependent glutathione peroxidase family, in addition to GSHPx-1, GSHPx-P, and phospholipid hydroperoxide glutathione peroxidase (PHGPX).
 ...
PMID:Expression, characterization, and tissue distribution of a new cellular selenium-dependent glutathione peroxidase, GSHPx-GI. 842 33

NADH oxidase (EC 1.6.99.3) was purified from cell lysates of Serpulina (Treponema) hyodysenteriae B204 by differential ultracentrifugation, ammonium sulfate precipitation, and chromatography on anion-exchange, dye-ligand-affinity, and size-exclusion columns. Purified NADH oxidase had a specific activity 119-fold higher than that of cell lysates and migrated as a single band during denaturing gel electrophoresis (sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE]). The enzyme was a monomeric protein with an estimated molecular mass of 47 to 48 kDa, as determined by SDS-PAGE and size-exclusion chromatography. Optimum enzyme activity occurred in buffers with a pH between 5.5 and 7.0. In the presence of oxygen, beta-NADH but not alpha-NADH, alpha-NADPH, or beta-NADPH was rapidly oxidized by the enzyme (Km = 10 microM beta-NADH; Vmax = 110 mumol beta-NADH min-1 mg of protein-1). Oxygen was the only identified electron acceptor for the enzyme. On isoelectric focusing gels, the enzyme separated into three subforms, with isoelectric pH values of 5.25, 5.35, and 5.45. Purified NADH oxidase had a typical flavoprotein absorption spectrum, with peak absorbances at wavelengths of 274, 376, and 448 nm. Flavin adenine dinucleotide was identified as a cofactor and was noncovalently associated with the enzyme at a molar ratio of 1:1. Assays of the enzyme after various chemical treatments indicated that a flavin cofactor and a sulfhydryl group(s), but not a metal cofactor, were essential for activity. Hydrogen peroxide and superoxide were not yielded in significant amounts by the S. hyodysenteriae NADH oxidase, indirect evidence that the enzyme produces water from reduction of oxygen with NADH. The N-terminal amino acid sequence of the NADH oxidase was determined to be MKVIVIGCHGAGTWAAK. In its biochemical properties, the NADH oxidase of S. hyodysenteriae resembles the NADH oxidase of another intestinal bacterium, Enterococcus faecalis.
 ...
PMID:Purification and characterization of NADH oxidase from Serpulina (Treponema) hyodysenteriae. 849 17

Oxidative modification of human low-density lipoprotein (LDL) is thought to play a major role in the development of atherosclerosis. Free hemin, hemoglobin, myoglobin, and horseradish peroxidase (HRP) were reported in different studies as promoters of LDL lipid oxidation. Based on our previous finding that hemin induced oxidative crosslinking of the LDL protein, apolipoprotein B (apo B) (Y. I. Miller and N. Shaklai (1994) Biochem. Mol. Biol. Int. 34, 1121-1129), we compared the ability of free hemin and the above hemoproteins to induce peroxidation modification of apo B using SDS-PAGE. The levels of the final products of lipid peroxidation were determined as thiobarbituric acid-reactive substances. Hemoglobin and myoglobin were found to be as active as free hemin and all these were much more active than the classic peroxidase HRP. Moreover, the products of oxidized apo B differed: hemoglobin, myoglobin, and hemin induced mostly covalent aggregates, while HRP caused fragmentation of apo B. Hemoglobin reactivity was expressed at low H2O2 concentrations even in the absence of molecular oxygen. Desferal, along with other antioxidants, inhibited the hemoglobin-induced LDL oxidation independently of its iron-chelating property. The high peroxidative reactivity of hemoglobin is explained by its ability (unlike HRP) to transfer the oxidative equivalents from the heme active site, through the globin, to LDL. The apo B radicals thus formed are terminated, yielding intermolecular crosslinked protein. It is suggested that small amounts of the highly reactive hemoglobin in plasma, suffice to trigger LDL protein oxidation (along with its lipid oxidation), thereby inflict the atherosclerosis precondition.
 ...
PMID:Hemoglobin induced apolipoprotein B crosslinking in low-density lipoprotein peroxidation. 861 Oct 31

Protoporphyrinogen oxidase (EC 1.3.3.4) catalyzes the six electron oxidation of protoporphyrinogen IX to protoporphyrin IX. The enzyme from the bacterium Myxococcus xanthus has been cloned, expressed, purified, and characterized. The protein has been expressed in Escherichia coli using a Tac promoter-driven expression plasmid and purified to apparent homogeneity in a rapid procedure that yields approximately 10 mg of purified protein per liter of culture. Based upon the deduced amino acid sequence the molecular weight of a single subunit is 49,387. Gel permeation chromatography in the presence of 0.2% n-octyl-beta-D-glucopyranoside yields a molecular weight of approximately 100,000 while SDS gel electrophoresis shows a single band at 50,000. The native enzyme is, thus, a homodimer. The purified protein contains a non-covalently bound FAD but no detectable redox active metal. The M. xanthus enzyme utilizes protoporphyrinogen IX, but not coproporphyrinogen III, as substrate and produces 3 mol of H2O2/mol of protoporphyrin. The apparent Km and kcat for protoporphyrinogen in assays under atmospheric concentrations of oxygen are 1.6 microM and 5.2 min-1, respectively. The diphenyl ether herbicide acifluorfen at 1 microM strongly inhibits the enzyme's activity.
 ...
PMID:Protoporphyrinogen oxidase of Myxococcus xanthus. Expression, purification, and characterization of the cloned enzyme. 862 4

Synechococcus PCC 7942, a cyanobacterium, possesses catalaseperoxidase as the sole hydrogen peroxide-scavenging system. The enzyme has been purified to electrophoretic homogenenity from the cells. The native enzyme had a molecular mass of 150 kDa and was composed of two identical subunits of molecular mass 79 kDa. The apparent Km value of the catalase activity for H2O2 was 4.2 +/- 0.27 mM and the kcat value was 2.6 x 10(4) s-1. The enzyme contained high catalase activity and an appreciable peroxidase activity with o-dianisidine and pyrogallol. The catalase activity was not inhibited by 3-amino-1,2,4-triazole but by KCN and NaN3 (apparent Ki values 19.3 +/- 0.84 and 20.2 +/- 0.95 microM respectively). The enzyme showed an absorption spectrum of typical protohaem and contained one protohaem molecule per dimer. The gene encoding catalase-peroxidase was cloned from the chromosomal DNA of Synechococcus PCC 7942. A 2160 bp open reading frame (ORF), coding a catalase-peroxidase of 720 amino acid residues (approx. 79.9 kDa), was observed. The deduced amino acid sequence coincided with that of the N-terminus of the purified enzyme and showed a remarkable similarity to those of a family of catalase-peroxidases of prokaryotic cells. Escherichia coli BL21 (DE3)plysS, harbouring a recombinant plasmid containing the catalase-peroxidase gene, produced a large amount of proteins that co-migrated on SDS/PAGE with the native enzyme. The recombinant enzyme showed the same ratio of catalase activity to peroxidase activity with o-dianisidine and the same Km for H2O2 as the native enzyme.
 ...
PMID:The catalase-peroxidase of Synechococcus PCC 7942: purification, nucleotide sequence analysis and expression in Escherichia coli. 864 14


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>