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)

Clinical and laboratory evaluations are reported on two patients with congenital goiter and hypothyroidism due to iodide organification defect. In one patient, a 31-year-old white male with severe mental retardation, administration of perchlorate caused discharge of 69% of the radioiodine accumulated in the thyroid gland. Thyroid tissue had negligible peroxidase activity in the tyrosine-iodinase, triliodide, and guaiacol assays. Preincubation of subcellular fractions with hematin restored activity. The restored enzyme was labile to high concentrations of H2O2 (5.6times 10-4 h2o2 produced inhibition in the triiodide assay). Heating of the enzyme for 5 min at 46 degrees C produced 50% inactivation, while higher temperatures were required to half-inactivate normal peroxidases. This case represents a second example of the "peroxidase apoenzyme-prosthetic group defect" causing congenital goiter. The second patient, an example of the "deficient peroxidase defect," was a 10-yr-old girl with 35% discharge of thyroidal radioiodine by perchlorate. Peroxidase activity in the goiter tissue was quantitatively decreased (10%-20% of normal values) but kinetically normal with respect to apparent Km for H2O2. Hematin had little effect on the enzyme. Peroxidase activity had abnormal subcellular distribution, since pellets sedimenting between 39,000 and 105,000 g contained most of the activity. Normal thyroglobulin was observed in the thyroid gland of the patient. Two distinct defects of the peroxidase system can produce congenital goiter by limiting organification of iodide.
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PMID:Differentiation of two abnormalities in thyroid peroxidase causing organification defect and goitrous hypothyroidism. 16 74

The enzymatic iodination technique has been utilized in a study of the externally disposed membrane proteins of the mouse L cell. Iodination of cells in suspension results in lactoperoxidase-specific iodide incorporation with no loss of cell viability under the conditions employed, less than 3% lipid labeling, and more than 90% of the labeled species identifiable as monoiodotyrosine. 90% of the incorporated label is localized to the cell surface by electron microscope autoradiography, with 5-10% in the centrosphere region and postulated to represent pinocytic vesicles. Sodium dodecylsulfate-polyacrylamide gels of solubilized L-cell proteins reveals five to six labeled peaks ranging from 50,000 to 200,000 daltons. Increased resolution by use of gradient slab gels reveals 15-20 radioactive bands. Over 60% of the label resides in approximately nine polypeptides of 80,000 to 150,000 daltons. Various controls indicate that the labeling pattern reflects endogenous membrane proteins, not serum components. The incorporated 125-I, cholesterol, and one plasma membrane enzyme marker, alkaline phosphodiesterase I, are purified in parallel when plasma membranes are isolated from intact, iodinated L cells. The labeled components present in a plasma membrane-rich fraction from iodinated cells are identical to those of the total cell, with a 10- to 20-fold enrichment in specific activity of each radioactive peak in the membrane.
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PMID:Externally disposed plasma membrane proteins. I. Enzymatic iodination of mouse L cells. 16 33

Purified membranes from surface-labelled phytohemagglutinin-resistant (Pha(R) and wild-type chinese hamster ovary cells have been analysed by sodium dodecyl sulphate gel electrophoresis. Gel patterns were compared for cells labelled via galactose oxidase and B-3H4 or lactoperoxidase and radioactive iodide. The results suggest that Pha-R cells are altered in the carbohydrate portion of a number of their membrane glycoproteins.
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PMID:Altered cell surface glycoproteins in phytohemagglutinin-resistant mutants of Chinese hamster ovary cells. 16 78

Lyosomal myeloperoxidase activity in human phagocytic leucocytes was stimulated by incubation with virulent (T1) and avirulent (T4) forms of Neisseria gonorrhoeae. The amount of activity, assayed by bacterial iodination (125-iodine) after 30 min. exposure to the pagocytes in the absence of serum, was about fifty times greater in cells infected with T4 strains. In the presence of heated human serum, or its IgG component, myeloperoxidase activity increased, but T1-Stimulated activity was significantly less than that of T4 and was not proportional to multiplicity of infection. From these results and from those of a previous study we conclude that T1 can stimulate leucocyte myeloperoxidase activity from an extracellular location, that for this activity a serum fraction is required, and that this may be a mechanism responsible for some of the killing of the membrane associated T1.
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PMID:Effect of infection with gonococci on myeloperoxidase activity of leucocytes. 16 24

The course of chlorination in neutrophilic granulocytes has been shown. The process of 36Cl incorporation occurs during and after the engulfment of bacteria by granulocytes. Incorported radioactivity was found in insoluble fractions. The myeloperoxidase obtained from neutrophils catalyzes chlorination of protein (bovine serum albumin) and bacteria (Staphylococcus epidermidis) in the presence of hydrogen peroxide and chloride. The products of chlorination are insoluble. Chlorination in neutrophils is inhibited by the iodide and myeloperoxidase inhibitors azide and cyanide. A quantitative method of determination of biological chlorination in cells has been devised.
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PMID:Chlorinating ability of human phagocytosing leucocytes. 17 Jan 1

The oxidase-peroxidase from Datura innoxia which catalyses the oxidation of formylphenylacetic acid ethyl ester to benzoylformic acid ethyl ester and formic acid was also found to catalyse the oxidation of NADH in the presence of Mn2+ and formylphenylacetic acid ethyl ester. NADH was not oxidized in the absence of formylphenylacetic acid ethyl ester, although formylphenylacetonitrile or phenylacetaldehyde could replace it in the reaction. The reaction appeared to be complex and for every mol of NADH oxidized 3-4 g-atoms of oxygen were utilized, with a concomitant formation of approx. 0.8 mol of H2O2, the latter being identified by the starch-iodide test and decomposition by catalase. Benzoylformic acid ethyl ester was also formed in the reaction, but in a nonlinear fashion, indicating a lag phase. In the absence of Mn2+, NADH oxidation was not only very low, but itself inhibited the formation of benzoylformic acid ethyl ester from formylphenylacetic acid ethyl ester. A reaction mechanism for the oxidation of NADH in the presence of formylphenylacetic acid ethyl ester is proposed.
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PMID:Oxidase-peroxidase enzymes of Datura innoxia. Oxidation of reduced nicotinamide-adenine dinucleotide in the presence of formylphenylacetic acid ethyl ester. 17 92

The granulocytes of a patient with generalized pustular psoriasis (GPP) were found to have impaired ability to fix iodine after ingestion of yeast particles. Since hexose monophosphate shunt (HMS) activity was increased and the contents of 3 other lysosomal enzymes, beta-glucuronidase, N-acetyl-beta-glucosaminidase and lysozyme, were within normal range, the impaired iodination appeared to be due to a selective defect of myeloperoxidase (MPO) activity within the phagocytic cells. The deficient iodination was accompanied by a decreased intracellular killing of E. coli and C. albicans. Since hexose monophosphate shunt activity was enhanced and azide and cyanide inhibited the intracellular killing of E. coli only moderately, the patient's granulocytes may possess azide- and cyanide-resistant, MPO-independant microbicidal systems coupled to the oxidative metabolism. Assessment of granulocyte iodination and enzyme contents of the relatives of the patient revealed no hereditary transmission. Since GPP is characterized by the development of subcorneal pustules containing granulocytes, the MPO-deficiency may be the cause of or enhance the development of the disease.
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PMID:Function of granulocytes with deficient myeloperoxidase-mediated iodination in a patient with generalized pustular psoriasis. 17 20

The thyroid gland of homozygous Gunn rats is moderately enlarged and displays a brownish-black discoloration. Light microscopic examination discloses that the follicular cells are filled with brown granules, which are shown, under the electron microscope, to be modified colloid droplets. Most of them possess a strong acid phosphatase and a mild peroxidase activity and contain a melanin-like pigment, according to histochemical analysis. In comparison with normal Wistar rats, Gunn rats possess significantly higher plasma thyroxine and lower triiodothyronine as well as an increased plasma TSH level. The soluble protein content of the thyroid is reduced in the Gunn rat, as is the total intrathyroid iodine content. The hyperthyroxinaemia of homozygous Gunn rats is due to a hereditary deficiency in hepatic glucuronyl transferase activity. The excess circulating thyroxine is of little functional importance because it is firmly bound to plasma proteins. But Gunn rats have a slight hypothyroid goitre for reasons not yet elucidated. The functional as well as morphological data at present available suggest a modified thyroid iodine metabolism and an altered composition of the thyroglobulin which may induce abnormalities in colloid proteolysis. The observed pigment may result from peroxidation of tyrosine. These alterations are probably independent of the sole enzymatic deficiency so far encountered in these animals and may probably be ascribed to a primary enzymatic defect in the thyroid gland itself.
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PMID:Pigmentation and dysfunction of Gunn rat thyroid: correlation between morphological and biochemical data. 17 74

A highly specific and simple radioimmunoassay for cyclic AMP with a sensitivity of 0.04 picomoles/tube has been developed according to the method of Steiner et al., using 125I-succinyl cyclic AMP tyrosine methyl ester as a tracer. The tracer with higher immunoactivities could be simply and constantly prepared by an enzymatic iodination procedure utilizing lactoperoxidase, radioactive iodide and hydrogen peroxide generated by glucose-glucose oxidase system, rather than by chloramine-T procedure.
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PMID:Enzymatic radioiodination of succinyl cyclic AMP tyrosine methyl ester by lactoperoxidase and radioimmunoassay for cyclic AMP. 18 59

Myeloperoxidase, H2O2, and a halide form a potent antimicrobial and cytotoxic system of the polymorphonuclear leukocyte. A cytotoxic effect of this system on human blood leukocytes is demonstrated, employing 51Cr release and dye exclusion assays. Cytotoxicity is dependent on enzymatically active myeloperoxidase, H2O2, or a peroxide-generating enzyme system and either chloride or iodide. Cell damage is rapid, with maximal levels of 51Cr release occurring within 30--60 min. Approximately equal sensitivity to the peroxidase system is observed for polymorphonuclear leukocytes and mononuclear leukocytes. Since myeloperoxidase and H2O2 are released from polymorphonuclear leukocytes under certain conditions, such as during particle ingestion, it is suggested that peroxidase-mediated leukocyte injury may be an important feature of the inflammatory response.
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PMID:Myeloperoxidase--H2O2--halide system: cytotoxic effect on human blood leukocytes. 19 41


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