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)

Myeloperoxidase (donor: hydrogen-peroxide oxidoreductase, EC 1.11.1.7) was isolated from leukocytes of patients with chronic granulocyte leukemia. In the presence of H2O2 and Cl- at pH 4.0-6.6 the myeloperoxidase catalyses chlorination of taurine to monochloramine taurine and simultaneously undergoes inactivation. The myeloperoxidase inactivation rate depends on the concentration of H2O2 and Cl-: both the initial rate of chlorination and myeloperoxidase inactivation rate increase with increasing concentration of H2O2. However, an increase in concentration of Cl- results in a decrease in enzyme inactivation. At a given H2O2 concentration, myeloperoxidase inactivation is a first order reaction, which implied that the enzyme may react with a substrate a limited number of times.
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PMID:Myeloperoxidase inactivation in the course of catalysis of chlorination of taurine. 20 Feb 71

The mechanism of the cytotoxic reaction of leukocytes to Trypanosoma dionisii was investigated. Cytotoxicity was measured by release of [99mTc]pertechnetate from labeled protozoa. Both granulocytes and lymphocytes were found to be cytotoxic to antibody-coated T. dionisii. The reaction was inhibited by diethyldithiocarbamate and by potassium cyanide, both of which inhibit myeloperoxidase. Myeloperoxidase from azurophil granules was toxic to T. dionisii, provided that hydrogen peroxide was also present. Hydrogen peroxide formation was induced in granulocytes and, to a lesser extent, in lymphocytes by antibody-coated T. dionisii. Inhibition of this hydrogen peroxide formation by treatment of the effector cell surface with p-diazobenzenesulfonic acid inhibited cytotoxicity. It is therefore concluded that granulocytes, and probably also lymphocytes, kill T. dionisii with hydrogen peroxide by a peroxidase-mediated reaction. Although hydrogen peroxide and myeloperoxidase alone were also cytotoxic to the lymphoblastoid cell line CLA4, it seems unlikely that this is the cytotoxic mechanism for this process because these cells were unable to induce hydrogen peroxide formation.
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PMID:Role of hydrogen peroxide and peroxidase in the cytotoxicity of Trypanosoma dionisii by human granulocytes. 21 88

Aldehyde-resistant, diaminobenzidine-stained endogenous peroxidases form ideal markers for the biochemical endpoints of hormone stimulation and differentiation of certain mammalian cells and tissues. The lactoperoxidase (LPO)-type of endogenous peroxidases are synthesized by the acinar cells of the salivary, Harderian, lacrimal and mammary glands and are present in their secretions. These LPO-type enzymes, that are inhibited by cyanide and aminotriazole, appear to operate extracellularly as bactericidal agents in milk and in other biological fluids. In the mammary gland, lactoperoxidase is a consistent marker enzyme for differentiated acinar cells engaged in lactogenesis. Myeloperoxidase (MPO)-type endogenous peroxidases are prominent markers for the GERL endomembrane system and differentiated lysosomes in certain cells of the reticuloendothelial system and phagocytes. MPO is prominent within eosinophils, peritoneal macrophages and in Kupffer cells. The MPO-type endogenous peroxidases function primarily within lysosomes as bactericidal agents. Thyroid peroxidase (TPO) is relegated to the cisternae of the granular endoplasmic reticulum and Golgi apparatus, to apical cytoplasmic vesicles and to the luminar cell membrane surface of acinar cells. The enzyme is probably activated at release and functions both in the organification reaction (T leads to To) and in the biosynthesis of thyroxine. Thyroid stimulating hormone (TSH) appears to play a key role in the regulation of TPO levels and activity in the thyroid gland. Certain tissues displaying growth-dependency on estrogen (i.e., uterus, cervix, vagina and the DMBA-induced rat mammary tumor) synthesize and secrete endogenous peroxidase into their lumina. These enzymes serve as important marker proteins of estrogen action, in that they occur distal to the binding of estrogen to its receptor protein. Estrogen antagonists, particularly CI-628 (Parke-Davis) and Nafoxidine (Upjohn) that appear to function through the estrogen receptor mechanism, also induce synthesis of the reproductive tract endogenous peroxidase but inhibit growth of these tissues. Progesterone antagonizes the synthesis of the reproductive tract peroxidases and inhibits growth of the tissues as well, in part, through the reduction of the cytosol estrogen receptor protein. Endogenous peroxidase activity appears to represent a reliable marker for rodent breast cancer tissues displaying dependency for estrogen and is of potential interest as a diagnostic marker protein in human breast cancer. Rat uterine peroxidase (UP) has been investigated by microelectrophoretic techniques. The molecular weight of UP has been determined in the range of 100,000 by using polyacrylamide gradient gels in the absence and presence of nonionic and anionic detergents. The isoelectric point of UP is located between pH 4.5 and 5.9. Employing the two-dimensional combination of isoelectric focusing and gel gradient electrophoresis, UP was separated into two subunits, one having a molecular weight of 70,000, the other less than 20,000.
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PMID:Mammalian endogenous peroxidases as cellular markers and as biosynthetic endpoints of hormone-mediated activity: viewpoint from cytochemistry. 22 20

Myeloperoxidase with an A420/280 ratio of 0,48 was prepared from normal human leucocytes. This partially purified preparation catalysed guaiacol oxidation, iodination of bovine serum albumin and de-iodination of 125I-thyroxine. Non-steroidal anti-inflammatory drugs (naproxen, indomethacin and flufenamic acid) showed a significant inhibitory effect on myeloperoxidase-catalysed iodination at concentrations of 10(-4)M and higher. Guaiacol also inhibited myeloperoxidase-catalysed iodination, and its iodination inhibition curve was nearly identical to that obtained with the anti-inflammatory drugs. At concentrations between 10(-3)M and 10(-7)M the antiinflammatory drugs had very little or no effect on thyroxine de-iodination. Flufenamic acid and indomethacin, however, inhibited de-iodination significantly at a concentration of 10(-2)M. It is postulated that non-steroidal anti-inflammatory drugs may inhibit myeloperoxidase-catalysed protein iodination by acting as oxidizable cofactors which compete with other oxidizable substrates for oxidants formed by the peroxidase-hydrogen peroxide complex. In view of this and because the myeloperoxidase-hydrogen peroxide system may be involved in inflammatory tissue damage, the possibility should be considered that the action of non-steroidal anti-inflammatory drugs is at least partly attributable to a radical scavenging effect or to sequestration of oxidants.
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PMID:Inhibitory effects of non-steroidal anti-inflammatory drugs on human myeloperoxidase. 22 74

The antibacterial effect of purified human salivary lactoperoxidase on a cariogenic strain of Streptococcus mutans was demonstrated while another oral peroxidase, probably of leukocytic origin, did not affect the growth. Lactoperoxidase was rapidly adsorbed by bacterial cells indicating the necessity of the contact between the enzyme and the cells before inhibition.
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PMID:Antibacterial effect of salivary peroxidases on a cariogenic strain of Streptococcus mutans. 27 83

Lactoperoxidase (EC 1.11.1.7) catalyzed cell surface radioiodination was employed to monitor the fate of murine B cell membrane (mem) IgM and IgD on radiolabeled cells in short-term culture. Both mem-IgM and mem-IgD were shed from the cell surface with biphasic kinetics. The rapid phase of mem-IgD shedding was somewhat slower (half-time = 12 hr) than that of mem-IgM shedding (half-time = 7-8 hr). The effect of temperature, colchicine, and cytochalasin on the shedding of the two membrane immunoglobulin isotypes was determined. The shedding of mem-IgD was more energy dependent than that of mem-IgM and was sensitive to colchicine but not cytochalasin. Conversely, the shedding of mem-IgM was sensitive to cytochalasin but not colchicine. The results suggest that the mechanisms of shedding of mem-IgM and mem-IgD are qualitatively distinct and may be regulated by microfilaments or microtubules, respectively.
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PMID:Differential effects of colchicine and cytochalasins on the shedding of murine B cell membrane IgM and IgD. 31 43

The antimicrobial activity of the lactoperoxidase, peroxide, thiocyanate system against Escherichia coli was directly related to the oxidation of bacterial sulfhydryls. Lactoperoxidase catalyzed the oxidation of thiocyanate, which resulted in the accumulation of hypothiocyanite ion, OSCN-. A portion of the bacterial sulfhydryls were oxidized by OSCN- to yield sulfenic acid and sulfenyl thiocyanate derivatives. The remaining sulfhydryls were not oxidized, although OSCN- was present in large excess. The oxidation of sulfhydryls to sulfenyl derivatives inhibited bacterial respiration. This inhibition could be reversed by adding sulfhydryl compounds to reduce the sulfenyl derivatives and the excess OSCN-. Also, this inhibition could be reversed by washing the cells so as to remove the excess unreacted OSCN-. After washing, the bacteria underwent a time-dependent recovery of their sulfhydryl content. This recovery resulted in recovery of the ability to respire. The inhibited cells were viable if diluted and plated shortly after the incubation with the lactoperoxidase, peroxide, thiocyanate system. On the other hand, long-term incubation in the presence of the excess OSCN- resulted in loss of viability. Also, the inhibition of respiration became irreversible. During this long-term incubation, the excess OSCN- was consumed and the sulfenyl derivatives disappeared.
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PMID:Lactoperoxidase, peroxide, thiocyanate antimicrobial system: correlation of sulfhydryl oxidation with antimicrobial action. 35 45

Reticulocytes were separated on the basis of density by isopycnic centrifugation in dextran gradients. This parameter was shown to correlate with the degree of maturity of the cells. Lactoperoxidase iodination of cells of different densities followed by sodium dodecyl sulfate (NaDodSO4) electrophoresis revealed a 190 000 molecular weight protein which was well labeled in early reticulocyte membranes. Efficiency of labeling decreased as the cells increased in density, and high specific activity iodination of mature erythrocytes did not result in the labeling of any species near this molecular weight. Inclusion of rabbit transferrin prior to the iodination procedure resulted in a specific loss of labeling of this 190 000 molecular weight species. When steps were taken to clear endogenous transferrin from the membranes, the labeling of this species was enhanced. These observations are consistent with the concept that transferrin can block the lactoperoxidase catalyzed iodination of this membrane protein by specifically associating with it. Coomassie blue and periodic acid-Schiff staining of NaDodSO4 gels of these membranes revealed that a glycoprotein present at this molecular weight is lost during the course of reticulocyte maturation. It is concluded from these studies that a glycoprotein of molecular weight 190 000 constitutes the transferrin receptor in the reticulocyte membrane.
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PMID:Identification of the transferrin receptor of the rabbit reticulocyte. 70 86

Whole saliva samples of volunteers who ate a strict diet for two years with regard to the type of sweeteners used (sucrose, fructose, and xylitol) showed considerable differences in the lactoperoxidase activity. The consumption of a xylitol diet increased the activity of this enzyme fourfold to tenfold when compared to the other two test groups. Lactoperoxidase belongs to the natural defense mechanisms of the oral cavity. However, the consumption of a xylitol diet also leads to a strong reduction in the incidence of dental caries. It is suggested that the xylitol-induced elevation of the salivary lactoperoxidase activity and the cariostatic properties of xylitol are partly interrelated phenomena.
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PMID:Xylitol-induced increase of lactoperoxidase activity. 77 61

Human saliva was incubated with human enamel powder, and the lactoperoxidase activity of the saliva was measured before and after incubation. Liquidphase lactoperoxidase activity was reduced in direct proportion to the weight of enamel powder added. Lactoperoxidase molecules were adsorbed to the enamel surface in an enzymatically active conformation, and this enamel-bound lactoperoxidase activity was also measured. The adsorption of lactoperoxidase was irreversible and produced at least a 40% increase in the concentration of lactoperoxidase in the enamel surface phase as compared with its concentration in the liquid phase. Enamel-bound lactoperoxidase, as well as the free enzyme, was capable of inactivating the key glycolytic enzyme hexokinase. The implications of the adsorption phenomenon for bacterial colonization are discussed.
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PMID:Enzyme activity of salivary lactoperoxidase adsorbed to human enamel. 88 9


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