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:1.11.1.7 (peroxidase)
65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Iodination of a non halogenated goiter thyroglobulin and the resulting thyroxinogenesis was studied in vitro with purified thyroid peroxidase, H2O2 generating system and various concentrations of iodide. The rate of iodination was linear during the first minutes of incubation but thyroxine synthesis only began after a lag period whatever the iodide concentration in the incubation medium was. With high iodide concentrations a highly iodinated thyroglobulin (40-50 iodine atoms) containing no thyroxine was obtained after 3 minutes of incubation. If this highly iodinated goiter thyroglobulin was purified and reincubated with peroxidase and H2O2, thyroxine synthesis was again observed only after a lag period (2-3 min). In the absence of iodide the enzyme to elicit thyroxine synthesis. Depending of its concentration free diiodotyrosine exerts two opposite effects on the reaction catalyzed by thyroid peroxidase : at high concentration (10(-4) M) in inhibition of thyroglobulin iodination, and at low concentration (10(-7), 10(-8) M) a stimulating effect on thyroid hormones biosynthesis.
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PMID:[Proceedings: In vitro thyroid hormone formation (author's transl)]. 119 Jul 29

1. Human tumour KB cells growing in suspension culture were labelled by lactoperoxidase-catalysed iodination. Several major radioactively labelled proteins were detected by poly-acrylamide-gel electrophoresis in sodium dodecyl sulphate. 2. After reduction with 2-mercaptoethanol the major radioactive electrophoretic bands migrated as substances with apparent molecular weights of about 90,000, 70,000, 60,000, 50,000 and 34,000 and corresponded closely to the positions at which the major glycosylated polypeptide subunits of KB-cell homogenates migrated during electrophoresis under the same conditions. 3. All the iodinated protein bands except one were present in purified preparations of KB plasma membranes. 4. Most of the 50,000-molecular-weight species, supposedly a surface protein component labelled during iodination of intact and viable KB cells by a non-penetrating enzyme reagent, appeared in a crude nuclear pellet during fractionation. 5. The glyco-protein nature of the major external iodinated species of KB cells was confirmed by adsorption chromatography of these substances, dissolved in low concentrations of Triton X-100, on a lectin-Sepharose column. Two major enzyme markers of the KB plasma membrane, 5'-nucleotidase and alkaline phosphatase were also found to be glycoproteins. 6. Enzyme-catalysed incorporation of radioactive iodine into a fraction of low molecular weight and soluble in chloroform-methanol mixtures also occurred during lactoperoxidase treatment of intact KB cells. The partial characterization of this fraction is briefly described.
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PMID:Surface labelling for human tumour KB cells. Iodination and fractionation of membrane glycoproteins. 120 Oct 9

The site of iodination of protein in the thyroid gland (whether intracellular or intraluminal) was ascertained by autoradiographic studies using iodide-125I. In tissue fixed within about 40 sec after intravenous injection of radioiodide the silver grains of autoradiographs were concentrated over the follicular lumen generally as a ring of grains close to the apical border of the follicular cells. The zone of grains was sharply limited toward the cells. No concentration of silver grains was detected associated with any intracellular organelle. The autoradiographic ring which had a minimum width of about 2 mum was continuous along the apical plasma membrane of the follicle cells but there was a drastic reduction in grain density along the plasma membrane of the distal portion of pseudopods. Tissue was fixed so soon after radioiodide injection that it appeared likely that a negligible fraction of radioiodoprotein, if formed in the cell, could have been transferred to the lumen. The observations strongly indicate that the iodination of thyroglobulin occurs in the follicle lumen, probably at the apical surface of the follicle cells. Since in the TSH-treated animals the distribution of the labeling along the apical plasma membrane agrees well with the reported histochemical distribution of thyroperoxidase in this membrane, it is further concluded that iodination may well be catalyzed by peroxidase in the apical plasma membrane.
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PMID:Site of iodination in the rat thyroid gland deduced from electron microscopic autoradiographs. 120 71

Cold thyroid nodules are generally due to impaired iodide uptake, while organification remains normal. In a case of a nodule appearing hot one hour after Tc99 m and cold 24 h after 131I-iodide, in vivo investigations showed that the trapping function was unimpaired and that the defect lay in organification. An early thyroid scan taken with 131I-iodide showed definite radioactivity in the nodule which was dischargeable by K perchlorate. This finding was confirmed by in vitro study of the tissue. Indirect evidence suggests that a defect was present in the H2O2 generating system rather than in peroxidase.
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PMID:Benign thyroid nodule with normal iodide trap and defective organification. 120 1

Two patients (G2, G3) with iodine organification defect were studied. The first patient (G2), a 25-year-old women with no clinical hypothyroidism, had had her goiter for 10 years; 62% of the thyroidal iodine was released by perchlorate indicating iodine organification defect. The thyroid tissue obtained at thyroidectomy contained a normal concentration of thyroid peroxidase (I2 formation from I-) when tested after solubilization of the enzyme by trypsin and digitonin treatment of the particulate material. 1. The enzymatic activity (G2-TPO) behaved on DEAE cellulose chromatography very differently from those of hog (P-TPO) or another human goiter peroxidase (G1-TPO) (Pommier, et al., J Clin Endocrinol Metab 39: 69, 1974): the molarity of elution was 2M NaCl instead of 0.15 mM. 2. Both P-TPO and G2-TPO catalyzed iodide peroxidation (I- leads to I2) but the Km (iodide) value for G2-TPO was much lower (2.3 x 10(-2) M) when compared with that of P-TPO (3.7 x 10(-3) M) or G1-TPO (3.5 x 10(-3) M). In addition, the optimum pH for this reaction differed markedly (pH 6.1 instead of 7.9). 3. G2-TPO was poorly efficient in catalyzing the oxidation of gaiacol to tetragaiacol. 4. G2-TPO was unable to perform the iodination of non-iodinated goiter thyroglobulin whatever the pH and the iodide concentration. 5. Thyroglobulin from this goiter (G2) was almost not iodinated (0.0014%), i.e., 0.07 atoms iodine/mole thyroglobulin), and its total content in the gland was very low (0.3-4 g/1000 g wet tissue instead of 25 g). A clear discrepancy was thus shown between the euthyroid state of this patient and the total lack of iodinating activity of the isolated peroxidase. The second patient (G3), a 17-year-old man with clinical hypothyroidism, had had his goiter for 5 years. 100% of the thyroidal iodine was released by perchlorate indicating a complete iodine organification defect. The thyroid tissue obtained at thyroidectomy contained no peroxidase activity when tested before and after treatment of the particulate material by trypsin and digitonin and even in the presence of hematin. Thyroglobulin from this goiter, which was almost non-iodinated (0.0014%), was present in normal amounts in the gland (congruent to 25 g/1000 g).
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PMID:Thyroid iodine organification defects: a case with lack of thyroglobulin iodination and a case without any peroxidase activity. 126 32

Iodination of staphylococcal alpha-toxin by the lactoperoxidase method resulted in the maximal incorporation of about 2.5 atoms of iodine per molecule of alpha-toxin. The iodination primarily involved a single tyrosine residue as shown by analysis of both cyanogen bromide and tryptic peptides. Iodination at a level of 1.2 iodine atoms per alpha-toxin molecule led to a dramatic decrease in the hemolytic and lethal activities, although no decrease in the binding of iodinated toxin to rabbit erythrocytes was observed (Cassidy and Harshman (1976), Biochemistry, the following paper in this issue). Monoiodinated alpha-toxin was found to have 15% of the specific hemolytic activity of native alpha-toxin. Incubation of rabbit erythrocytes with iodinated alpha-toxin led to a significant protection from the hemolytic activity of native alpha-toxin added later. The results show the modification of a single unique tyrosyl residue in alpha-toxin permits the resolution of alpha-toxin's biological activities from its cell binding activity.
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PMID:Iodination of a tyrosyl residue in staphylococcal alpha-toxin. 127 41

We localized alpha-smooth muscle actin (alpha-SMA) in the quail ovary, using the peroxidase-anti-peroxidase technique. Special attention was paid to the influence of fixation on the immunoreactivity of the antigen. The immunostaining of alpha-SMA largely depended on the nature of the fixative. The antigen could most successfully be localized in ovaries fixed in Carnoy's fluid. We also localized alpha-SMA and desmin in semi-thin glycol methacrylate sections of the pre-ovulatory follicle, using the immunogold-silver staining method. The sections were pretreated with Lugol's iodine or sodium metaperiodate to enhance the immunoreactivity. alpha-SMA was demonstrated in the cells of the chordae, the tunica albuginea, and the theca externa of each follicle. These structures were inter-connected, forming an ovarian suspensory apparatus. The thecal cells of prelampbrush follicles also expressed alpha-SMA. In the wall of the pre-ovulatory follicle, desmin was found in the cells of the chordae and the tunica albuginea, and in a few cells of the theca externa. In the theca interna, desmin, and sometimes alpha-SMA, was observed in cells adjacent to the endothelium of sinusoids, which are probably pericytes. Our results support the hypothesis that in birds the ovarian follicles possess a thecal contractile system, that is presumably involved in the ovulatory process.
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PMID:Immunolocalization of smooth muscle-like cells in the quail ovary. 128 32

The susceptibility of Candida albicans (ATCC 10231 and wild strains) to hypo(pseudo)halous ions (OSCN-, OBr-, OI-) produced by the lactoperoxidase system was tested. Six strains of Candida albicans were isolated from swabs taken from the mouths of children with orthodontic appliances and selected on Sabouraud-Chloramphenicol-Actidione agar plates. The survival rate of Candida blastospores after a 30 min exposure to lactoperoxidase system ranged from 79 to 105% in the presence of 615 microM thiocyanate, from 56 to 88% in the presence of 345 microM bromide and from 0 to 4% in the presence of 250 microM iodide. Results showed that only OI- could exert a strong inhibiting effect in vitro on Candida albicans at physiological concentrations. Nevertheless, the activity of the hypoiodite generating system in saliva was found to be under the control of thiocyanate concentration.
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PMID:Susceptibility of Candida albicans to peroxidase-catalyzed oxidation products of thiocyanate, iodide and bromide. 130 88

Degradation of methyl mercury (MeHg) and ethyl Hg (EtHg) with reactive oxygens was studied in vitro by using peroxidase-hydrogen peroxide (H2O2)-halide and rose bengal-ultraviolet light A systems. For this purpose, the direct determination method for inorganic Hg was employed. Both systems could effectively degrade EtHg, and MeHg to some extent. Degradation of MeHg and EtHg with the myeloperoxidase (MPO)-H2O2-chloride system was inhibited by MPO inhibitors (cyanide and azide), catalase, hypochlorous acid (HOCI) scavengers (glycine, alanine, serine and taurine), 1,4-diazabicyclo[2,2,2]octane and 2,5-dimethylfuran, but not by hydroxyl radical scavengers (ethanol and mannitol). Iodide was more effective than chloride as the halide component. Lactoperoxidase (LPO) could substitute for MPO in the iodide, but not the chloride system. With MPO-H2O2-chloride, MPO-H2O2-iodide and LPO-H2O2-iodide systems, we observed the increased degradation of EtHg in deuterium oxide (D2O) medium better than that in H2O medium. The D2O effect upon MeHg degradation was extremely weak. These results suggested that HOCl (or HOI) might be also capable of degrading MeHg and EtHg, besides the hydroxyl radical already reported by us. Singlet oxygen could degrade EtHg but not MeHg.
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PMID:Degradation of methyl and ethyl mercury into inorganic mercury by other reactive oxygen species besides hydroxyl radical. 131 15

Crystals suitable for X-ray diffraction analysis of both glycosylated and non-glycosylated forms of a barley peroxidase have been grown. The crystals of the glycosylated peroxidase have been grown by the hanging drop vapour diffusion method using polyethylene glycol 4000 as the precipitant in the presence of n-propanol and potassium iodide at pH 8.5. The crystals are needles belonging to the orthorhombic spacegroup P2(1)2(1)2(1) with unit cell dimensions a = 62.95 A, b = 66.24 A and c = 70.78 A. There is one barley peroxidase molecule in the asymmetric unit. The crystals contain approximately 38% solvent and appear to be stable to lengthy X-ray exposure. They diffract to beyond 1.9 A.
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PMID:Crystallization and preliminary X-ray diffraction studies of a peroxidase from barley grain. 133 35


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