scholarly journals Spectroscopic evidence for a photosensitive oxygenated state of ammonia mono-oxygenase

1985 ◽  
Vol 226 (2) ◽  
pp. 499-507 ◽  
Author(s):  
J H Shears ◽  
P M Wood
Keyword(s):  
Metal Ion ◽  
Chelating Agents ◽  
Ammonia Oxidation ◽  
Resting Cells ◽  
Organic Substrates ◽  
Copper Proteins ◽  
Binuclear Copper ◽  
Oxidation Activity ◽  
Copper Site ◽  
Electron Reduction

Photoinactivation of ammonia oxidation by Nitrosomonas europaea cells by near-u.v. light was confirmed and further shown to occur with the same rate constant as loss of bromoethane-oxidation activity. Hydroxylamine oxidation was much less photosensitive. Protection against inactivation was afforded by anaerobiosis, organic substrates of ammonia mono-oxygenase such as bromoethane, or metal-ion-chelating agents such as thiourea. The presence of 10 mM-NH4+ or 1 mM-hydroxylamine made little difference, whereas hydrazine had a potentiating effect. Illumination of cells also caused a bleaching in the absorption spectrum around 380 nm, along with changes in the cytochrome gamma-band region. Similar effects below 400 nm were obtained when organic substrates and inhibitors of the mono-oxygenase were added to cells in the dark. The copper proteins haemocyanin and tyrosinase have a photosensitive oxygenated state with a near-u.v. absorption band of similar half-width. They also have a sensitivity to chelating agents similar to that of ammonia mono-oxygenase. The experimental results are explained in terms of a three-stage catalytic cycle analogous to that for tyrosinase. In resting cells most of the enzyme is believed to be in an oxygenated (Oxy) form, which absorbs maximally at 378 nm and is photosensitive. In the presence of a substrate, one O atom is inserted into the substrate and the other is reduced to water, leaving the enzyme in an oxidized (Met) state. This is followed by a two-electron reduction of the proposed binuclear copper site to give a reduced (Deoxy) state, which can bind O2 to complete the cycle.

scholarly journals Responses to Ecopollutants and Pathogenization Risks of Saprotrophic Rhodococcus Species

Pathogens ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 974
Author(s):  
Irina B. Ivshina ◽  
Maria S. Kuyukina ◽  
Anastasiia V. Krivoruchko ◽  
Elena A. Tyumina
Keyword(s):  
Survival Strategies ◽  
Complex Life Cycle ◽  
Anthropogenic Pressure ◽  
Resting Cells ◽  
Organic Substrates ◽  
Negative Effects ◽  
Anthropogenic Pollutants ◽  
Rhodococcus Species ◽  
Wide Range ◽  
Rigid Cell Wall

Under conditions of increasing environmental pollution, true saprophytes are capable of changing their survival strategies and demonstrating certain pathogenicity factors. Actinobacteria of the genus Rhodococcus, typical soil and aquatic biotope inhabitants, are characterized by high ecological plasticity and a wide range of oxidized organic substrates, including hydrocarbons and their derivatives. Their cell adaptations, such as the ability of adhering and colonizing surfaces, a complex life cycle, formation of resting cells and capsule-like structures, diauxotrophy, and a rigid cell wall, developed against the negative effects of anthropogenic pollutants are discussed and the risks of possible pathogenization of free-living saprotrophic Rhodococcus species are proposed. Due to universal adaptation features, Rhodococcus species are among the candidates, if further anthropogenic pressure increases, to move into the group of potentially pathogenic organisms with “unprofessional” parasitism, and to join an expanding list of infectious agents as facultative or occasional parasites.

scholarly journals Hypochlorite and superoxide radicals can act synergistically to induce fragmentation of hyaluronan and chondroitin sulphates

2004 ◽  
Vol 381 (1) ◽  
pp. 175-184 ◽  
Author(s):  
Martin D. REES ◽  
Clare L. HAWKINS ◽  
Michael J. DAVIES
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Transition Metal Ions ◽  
Chloride Ions ◽  
Superoxide Radicals ◽  
Thermal Source ◽  
Site Specific ◽  
Trace Metal Ions ◽  
Electron Reduction ◽  
Polymer Fragmentation

Activated phagocytes release the haem enzyme MPO (myeloperoxidase) and also generate superoxide radicals (O2•−), and hence H2O2, via an oxidative burst. Reaction of MPO with H2O2 in the presence of chloride ions generates HOCl (the physiological mixture of hypochlorous acid and its anion present at pH 7.4). Exposure of glycosaminoglycans to a MPO–H2O2–Cl− system or reagent HOCl generates long-lived chloramides [R-NCl-C(O)-R′] derived from the glycosamine N-acetyl functions. Decomposition of these species by transition metal ions gives polymer-derived amidyl (nitrogen-centred) radicals [R-N•-C(O)-R′], polymer-derived carbon-centred radicals and site-specific strand scission. In the present study, we have shown that exposure of glycosaminoglycan chloramides to O2•− also promotes chloramide decomposition and glycosaminoglycan fragmentation. These processes are inhibited by superoxide dismutase, metal ion chelators and the metal ion-binding protein BSA, consistent with chloramide decomposition and polymer fragmentation occurring via O2•−-dependent one-electron reduction, possibly catalysed by trace metal ions. Polymer fragmentation induced by O2•− [generated by the superoxide thermal source 1, di-(4-carboxybenzyl)hyponitrite] was demonstrated to be entirely chloramide dependent as no fragmentation occurred with the native polymers or when the chloramides were quenched by prior treatment with methionine. EPR spin-trapping experiments using 5,5-dimethyl1-pyrroline-N-oxide and 2-methyl-2-nitrosopropane have provided evidence for both O2•− and polymer-derived carbon-centred radicals as intermediates. The results obtained are consistent with a mechanism involving one-electron reduction of the chloramides to yield polymer-derived amidyl radicals, which subsequently undergo intramolecular hydrogen atom abstraction reactions to give carbon-centred radicals. The latter undergo fragmentation reactions in a site-specific manner. This synergistic damage to glycosaminoglycans induced by HOCl and O2•− may be of significance at sites of inflammation where both oxidants are generated concurrently.

Photoinactivation of Agaricus bisporus tyrosinase: modification of the binuclear copper site

Biochemistry ◽  
1983 ◽  
Vol 22 (21) ◽  
pp. 4949-4953 ◽  
Author(s):  
David C. Fry ◽  
Kenneth G. Strothkamp
Keyword(s):  
Agaricus Bisporus ◽  
Binuclear Copper ◽  
Copper Site

scholarly journals Chelation and Metal-Ion Complex Formation of Chitosan Treated Cotton

2019 ◽  
Vol 8 (3) ◽  
pp. 93-100 ◽  
Author(s):  
Sudirman Habibie
Keyword(s):  
Cotton Fabric ◽  
Metal Ion ◽  
Chelating Agents ◽  
Transition Metal Ions ◽  
Cotton Fabrics ◽  
Carboxyl Groups ◽  
Polycarboxylic Acid ◽  
Salt Solutions ◽  
Polycarboxylic Acids ◽  
Zinc Salts

Chitin dan chitosan adalah bahan “chelate” yang sangat kuat untuk ion transisi logam terutama tembaga, nikel dan merkuri, dan sifat-sifat ini yang akan intensif di bahas. Pada studi ini kain kapas (cotton) dikerjakan dengan larutan chitosan-asam polikarboksilat untuk memperoleh kain kapas-chitosan yang mengandung gugus group karboksilat (-COOH) dan gugus amina (-NH2) fungsional. Penggunaan asam polykarboksilat (asam sitrat dan maleik) pada pelarutan chitosan menghasilkan group karboksil 0,5 meqs/g pada kain yang dicelup dengan larutan chitosan asam karboksilat. Kemudian kain kapas yang telah mengandung gugus karboksilat dan gugus amina ini dicelupkan pada larutan garam logam (garam tembaga dan seng). Terbukti bahwa larutan garam tembaga (copper) memberikan warna biru pada kain, hal ini mengindikasikan telah terjadi reaksi kompleks atau “Chelate”. Implikasi dari hasil ini maka diperkirakan kandungan group karboksil dan amina ini akan mempengaruhi pada pencelupan kain, namun hal ini tidak diuji.Kata kunci : Chitosan, Kain Kapas, Chelate, Asam asetat, Asam citrate, Asam maleik, Tembaga sulphate, Tembaga acetate.AbstractChitin and chitosan are powerfull chelating agents for transition metal ions, particularly copper, nickel and mercury, and these properties have been extensively reviewed. In this study, cotton fabric has been treated with chitosan- polycarboxylic acid solution to form chitosan treated cotton fabric containing carboxyl (-COOH) and amine (-NH2) functional groups. The use of polycarboxylic acids (citric and maleic acids) to dissolve chitosan has given carboxyl groups 0.5 meqs/g into chitosan treated cotton fabrics. Instead, the complexing of the treated cotton samples with copper and zinc salts was examined. The copper salt solutions gave blue fabrics confirming easily that complexing or chelation had occurred. There are implications for dyeing cotton making use of these groups but this was not investigated.Keyword : Chitosan, Cotton fabric, Chelation, Acetic acid, Citric acid, Maleic acid, Copper (II) sulphate, Copper (II) acetate.

Nitrogen–Sulfur Ligand Systems via Reduction of Schiff's Base – Zinc Complexes Derived from Benzothiazolines

1974 ◽  
Vol 52 (7) ◽  
pp. 1054-1058 ◽  
Author(s):  
James L. Corbin ◽  
Dale E. Work
Keyword(s):  
Sodium Borohydride ◽  
Metal Ion ◽  
Chelating Agents ◽  
Chloroform Solution ◽  
Zinc Complexes ◽  
Schiff’S Base ◽  
Simple Route ◽  
Sulfur Ligand

The coordinated imine groups of the Schiff's base – zinc complexes derived from various 2-substituted benzothiazolines are easily reduced with sodium borohydride to the corresponding amines. Removal of the metal ion from these reduced complexes yields the free ligands, providing a simple route to novel aminomercaptan chelating agents. Compounds of bi-, tri-, and tetradentate types were prepared in this manner.Evidence is given for a disproportionation of 2,2′-dimethyl-2,2′-bibenzothiazolinyl into 2-methylbenzothiazoline and 2-methylbenzothiazole in chloroform solution.

scholarly journals Modification of plasma proteins by cigarette smoke as measured by protein carbonyl formation

1992 ◽  
Vol 286 (2) ◽  
pp. 607-611 ◽  
Author(s):  
A Z Reznick ◽  
C E Cross ◽  
M L Hu ◽  
Y J Suzuki ◽  
S Khwaja ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Human Plasma ◽  
Gas Phase ◽  
Cigarette Smoke ◽  
Plasma Proteins ◽  
Metal Ion ◽  
Chelating Agents ◽  
Protein Carbonyl ◽  
Plasma Damage ◽  
Carbonyl Formation

Exposure of human plasma to gas-phase (but not to whole) cigarette smoke (CS) produces oxidative damage to lipids [Frei, Forte, Ames & Cross (1991) Biochem. J. 277, 133-138], which is prevented by ascorbic acid. The ability of CS to induce protein damage was measured by the carbonyl assay and by loss of enzyme activity and protein -SH groups. Both whole and gas-phase CS caused formation of carbonyls in human plasma, which was partially inhibited by GSH but not by ascorbic acid or metal-ion-chelating agents. Isolated albumin exposed to CS showed much faster carbonyl formation (per unit protein) than did whole plasma; damage to isolated albumin was partially prevented by chelating agents. Isolated creatine kinase (CK) lost activity upon exposure to CS much faster than did CK in plasma. Direct addition to plasma of mixtures of some or all of the aldehydes reported to be present in CS caused protein carbonyl formation and inactivation of CK, but neither occurred to the extent produced by CS exposure.

Is phenolate oxygen of a tyrosine resideu the bridging lingad at the binuclear copper site in oxyhemocyanin?

1981 ◽  
Vol 56 ◽  
pp. L33-L34 ◽  
Author(s):  
Jun Kino ◽  
Shinnichiro Suzuki ◽  
Wasuke Mori ◽  
Akitsugu Nakahara
Keyword(s):  
Binuclear Copper ◽  
Copper Site
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