Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.11.1.7 (peroxidase)
 65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A kinetic study has been carried out over the pH range of 2.63-9.37 for the reaction of horseradish peroxidase with hydrogen peroxide to form compound I of th;e enzyme. Analysis of the results, indicates that there are two kinetic influencing, ionizable groups on the enzyme with pKa values of 3.2 and 3.9. Protonation of these groups results in a decrease in the rate of reaction of the enzyme with H2O2. A previous study of the kinetics of cyanide binding to horseradish peroxidase (Ellis, W.D. & Dunford, H.B.: Biochemistry 7, 2054-2062 (1968)) has been extended to down to pH 2.55, and analysis of these results also indicates the presence of two kinetically important ionizable groups on the enzyme with pKa values of 2.9 and 3.9.
 ...
PMID:A kinetic study of the reaction of horseradish peroxidase with hydrogen peroxide. 23 15

The influence on diaminobenzidine staining of four variables: prefixation in aldehyde, temperature and pH of incubation, and H2O2 concentration, was investigated in catalase-, as well as in peroxydase-containing material. Catalase from five different sources and five types of peroxidase were examined. It is concluded: (a) when cells are incubated without prior fixation, in a DAB medium at room temperature and pH 7.3 with 0.003% H2O2, peroxidases produce a visible cytochemical stain, while catalases do not; (b) the cytochemical reaction elicited by catalases is stimulated by prior aldehyde fixation in specified conditions, and incubation at 45 degrees C and pH 9.7 with 0.06% H2O2; (c) under the latter circumstances several peroxidases also stain. Ultrastructural preservation is satisfactory in tissues incubated prior to fixation.
 ...
PMID:Cytochemical discrimination between catalases and peroxidases using diaminobenzidine. 23 53

The luciferase of the bioluminescent boring mollusc, Pholas dactylus, has been purified by a new method which includes centrifugation in cesium chloride gradients. Homogeneous preparations have been obtained and molecular weight determinations and subunit analysis support the idea that this preparation is an oxyluciferin-luciferase complex. The preparation catalyzes oxidation of ascorbic acid in presence of H2O2, and this peroxidase activitity has been used for characterization (thermal and pH stabilities, activity as a function of pH, isoelectric point, turnover number). The existence of two atoms of copper has been established and their involvement in the peroxidase activity indicated. Chemical analyses have shown that Pholad luciferase is a glycoprotein and the existence of glucosamine, fucose, mannose, and galactose residues has been demonstrated. The apparent buoyant dentisty (1.340), the sedimentation coefficient (10.7 S), the Stoke's radius (83 A), the partial specific volum (0.707), and the molecular weight (350,000) have been determined. The frictional ratio (flf0 = 1.8) derived from the Stoke's radius indicates that the molecule is asymmetric. The quaternary structure has been examined. Subunits of molecular weight 150,000 and 46,000 have been observed. The latter has electrophoretic properties identical with luciferin or oxyluciferin.
 ...
PMID:Characterization and properties of Pholas luciferase as a metalloglycoprotein. 23 92

The chromogen ABTS is the di-ammonium salt of 2,2'-azino-di[3-ethyl-benzthiazolin-sulfonic acid (6)] routinely used in the "glucose-oxidase assay" with the peroxidase (GOD-Perid method, Boehringer). 1. The specific property of ABTS to give a stable radical cation by oxidation with hydrogen peroxide in the presence of peroxidase was used to design a kinetic method, for enzyme-activity determinations. 2. The assay is suitable for the specific oxido-reductase using oxygen as acceptor, known also as "aerobic transhydrogenases" which are H2O2 formers (EC 1.-.3.-). 3. L-Amino acid: oxygen oxidoreductase (deaminating) (EC 1.4.3.2), was used throughout, being a representative model for such determinations.
 ...
PMID:[A kinetic method for the determination of the activity of "aerobic transhydrogenases" (author's transl)]. 24 20

The peroxidase activity of deuterohemin and deuterohemin complexes relative to the substrates pyrogallol and ascorbic acid was studied using d.c. polarography in aqueous solution. Imidazole and pyridine served as complex ligands. In the absence of the ligands, a continual rise in the substrate conversion rate with increasing H2O2 initial concentration is observed. Imidazole or pyridine were found to considerably increase the peroxidase activity of deuterohemin at low H2O2 concentrations. At high H2O2 concentrations, the dependence of the reaction rate on H2O2 concentration shows a bend, the reaction rate being in each case higher than that of free hemin under the same conditions. The reason of this fact is discussed to be a retarded formation of activated H2O2 hemin-ligand complexes at high H2O2 concentrations.
 ...
PMID:[Polarographic studies on the peroxidase activity of liganded deuterohemin]. 24 68

Purified milk lactoperoxidase and endogenous human salivary peroxidase were used to label the proteins of whole mouth saliva with [125I]iodide. The proteins were then analyzed by isoelectric focusing or they were subjected to one-dimensional polyacrylamide gel electrophoresis at pH 8.4. The radioactivity of the resolved protein fractions was determined. There were three to four major and four to five minor areas of radioactivity which were carried together with more or less distinctive protein fractions. Amylase and albumin were shown to be the most effective in binding [125I]iodide. No significant differences were observed in the iodination patterns of salivary proteins iodinated in the presence of endogenous saliva peroxidase and those iodinated in the presence of added milk lactoperoxidase. Hydrogen peroxide was necessary for iodination to take place. The significance of iodoproteins and the role of salivary peroxidases in the nonthyroidal metabolism of iodine are discussed.
 ...
PMID:Enzymatic iodination of salivary proteins by the 125I-lactoperoxidase system. 26 76

Physiological activity of lactoperoxidase and in vivo concentration of thiocyanate ions were shown to be inhibitory against a cariogenic strain of Streptococcus mutans. However, the amount of H2O2 in vivo may be too low for optimum inhibition by lactoperoxidase system. H2O2 alone also inhibited the growth of S mutants to some degree.
 ...
PMID:The antibacterial action of the various components of the lactoperoxidase system on a cariogenic strain of Streptococcus mutans. 27 82

Addition of beta-lapachone to the epimastigote (culture) form of Trypanosoma cruzi, suspended in saline, buffered-isotonic medium (pH 7.2), determined the appearance of large amounts of H2O2 in the suspension medium, as measured spectrophotometrically by formation of the H2O2 horse radish peroxidase complex. Under similar conditions, alpha-lapachone did not induce H2O2 formmation. Using NADH as electron donor, beta-lapachone (not alpha-lapachone) increased significantly the rate of H2O2 generation by epimastigote homogenates and the same occurred with NADPH, although in a reduced extent. Similar results were obtained with the isolated mitochondrial and microsomal fractions although with the latter NADPH was more effective than NADH as electron donor for beta-lapachone reduction and peroxide generation. The distribution of peroxide generation in epimastigote fractions would indicate that about 92% of the beta-lapachone dependent formation of peroxide occurred in the mitochondria, and 8% in the endoplasmic reticulum. The growth of epimastigotes was inhibited 95% by 1 microgram/ml beta-lapachone, a concentration that determined maximal rate of H2O2 production. Since H2O2 and other intermediates of oxygen reduction such as O2- (superoxide anion) and OH (hydroxyl radical) are lethal to cells and tissues, it is possible that the effect of beta-lapachone on T. cruzi proliferation in vitro was mediated by H2O2 and related free radicals.
 ...
PMID:[Effect of beta and alpha-lapachone on the production of H202 and on the growth of Trypanosoma cruzi]. 33 93

Conjugation of lysozyme with horse radish peroxidase by means of glutaraldehyde results in a complex which retains the activities of both enzymes. The incubation of peptidoglycan with lysozyme-peroxidase followed by the reaction with 3,3'-diaminobenzidine and H2O2 results in a strong labelling of both sides. In contrast, after treatment with peroxidase alone no reaction was observed. Thus, the specific binding of lysozyme-peroxidase can be used for the electron microscopic localization of this component in the bacterial cell wall. Isolated peptidoglycane as well as trypsinized cell walls of group A and C streptococci were labelled both on the inner and the outer surface. The surface of intact cells of group A- and C-streptococci was labelled only sparsely. In contrast, by means of the indirect immunoferritin technique strong labelling of intact cells was effected with specific anti-peptidoglycan antibodies. The specificity of these antibodies are mainly directed to the peptide side chains. From this we suggest that in the cell wall of group A and C streptococci the lysozyme-sensitive part of the peptidoglycan is not so superficially localized as the peptides.
 ...
PMID:The use of lysozyme-peroxidase-conjugates for the electron microscopic detection of peptidoglycan in the cell wall of streptococci. 35 34

Intrinsic tissue peroxidase activity can be more or less successfully destroyed by methanol-H2O2 treatment. It has been found, however, in our laboratory that horseradish peroxidase (HRP) coupled to antibody will bind to some tissue components on a nonspecific basis and remain to take part in the histochemical stain. This contributes considerably to the background. This difficulty can be largely overcome if the tissues are pretreated with a solution of horseradish peroxidase which binds with nonspecific tissue sites. The adsorbed enzyme, along with the intrinsic peroxidase, can then be successfully inactivated by methanol-H2O2 treatment. By this method of blocking, there is considerable reduction in background staining.
 ...
PMID:Use of horseradish peroxidase to block nonspecific enzyme uptake in immunoperoxidase microscopy. 35 48


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