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At least 973 records · Page 54Linked to original sources
PubMed2000

A hydrogen peroxide-forming NADH oxidase that functions as an alkyl hydroperoxide reductase in Amphibacillus xylanus.

The Amphibacillus xylanus NADH oxidase, which catalyzes the reduction of oxygen to hydrogen peroxide with beta-NADH, can also reduce hydrogen peroxide to water in the presence of free flavin adenine dinucleotide (FAD) or the small disulfide-containing Salmonella enterica AhpC protein. The enzyme has two disulfide bonds, Cys128-Cys131 and Cys337-Cys340, which can act as redox centers in addition to the enzyme-bound FAD (K. Ohnishi, Y. Niimura, M. Hidaka, H. Masaki, H. Suzuki, T. Uozumi, and T. Nishino, J. Biol. Chem. 270:5812-5817, 1995). The NADH-FAD reductase activity was directly dependent on the FAD concentration, with a second-order rate constant of approximately 2.0 x 10(6) M(-1) s(-1). Rapid-reaction studies showed that the reduction of free flavin occurred through enzyme-bound FAD, which was reduced by NADH. The peroxidase activity of NADH oxidase in the presence of FAD resulted from reduction of peroxide by free FADH(2) reduced via enzyme-bound FAD. This peroxidase activity was markedly decreased in the presence of oxygen, since the free FADH(2) is easily oxidized by oxygen, indicating that this enzyme system is unlikely to be functional in aerobic growing cells. The A. xylanus ahpC gene was cloned and overexpressed in Escherichia coli. When the NADH oxidase was coupled with A. xylanus AhpC, the peroxidase activity was not inhibited by oxygen. The V(max) values for hydrogen peroxide and cumene hydroperoxide reduction were both approximately 150 s(-1). The K(m) values for hydrogen peroxide and cumene hydroperoxide were too low to allow accurate determination of their values. Both AhpC and NADH oxidase were induced under aerobic conditions, a clear indication that these proteins are involved in the removal of peroxides under aerobic growing conditions.

Amino Acid Sequence↗
PubMed2004

Biodecolorization of azo, anthraquinonic and triphenylmethane dyes by white-rot fungi and a laccase-secreting engineered strain.

One laccase-secreting engineered strain and four white-rot fungi were tested for their capacity to decolorize nine dyes that could be classified as azo, anthraquinonic and triphenylmethane dyes. Trametes versicolor was the most efficient of the tested strains under these experimental conditions. Anthraquinonic dyes were decolorized more easily than the other two types. Small structural differences among the dyes could significantly affect decolorization. None of the strains showed lignin peroxidase or veratryl alcohol oxidase activity. None of the dyes were decolorized completely by laccase alone. It is likely that other phenoloxidases, such as Mn-dependent and versatile peroxidase, were also involved in decolorization of the dyes.

Anthraquinones↗
PubMed1999

Multiple transcription factors of the FNR family in denitrifying Pseudomonas stutzeri: characterization of four fnr-like genes, regulatory responses and cognate metabolic processes.

Pseudomonas stutzeri is a facultative anaerobic bacterium with the capability of denitrification. In searching for regulators that control the expression of this trait in response to oxygen withdrawal, we have found an unprecedented multiplicity of four genes encoding transcription factors of the FNR family. The fnrA gene encodes a genuine FNR-type regulator, which is expressed constitutively and controls the cytochrome cbb3-type terminal oxidase (the cco operon), cytochrome c peroxidase (the ccp gene) and the oxygen-independent coproporphyrinogen III oxidase (the hemN gene), in addition to its previously demonstrated role in arginine catabolism (the arc operon). The fnr homologues dnrD, dnrE and dnrS encode regulators of a new subgroup within the FNR family. Their main distinctive feature is the lack of cysteine residues for complexing the [4Fe-4S] centre of redox-active FNR-type regulators. However, they form a phylogenetic lineage separate from the FixK branch of FNR proteins, which also lack this cysteine signature. We have studied the expression of the dnr genes under aerobic, oxygen-limited and denitrifying conditions. DnrD is a key regulator of denitrification by selective activation of the genes for cytochrome cd1 nitrite reductase and NO reductase. The dnrD gene is part of the 30 kb region carrying denitrification genes of P. stutzeri. Transcription of dnrD was activated in O2-limited cells and particularly strongly in denitrifying cells, but was not under the control of FnrA. In response to denitrifying growth conditions, dnrD was transcribed as part of an operon together with genes downstream and upstream of dnrD. dnrS was found about 9 kb upstream of dnrD, next to the nrdD gene for anaerobic ribonucleotide reductase. The transcription of dnrS required FnrA in O2-limited cells. Mutation of dnrS affected nrdD and the expression of ferredoxin I as an element of the oxidative stress response. The dnrE gene is part of the nar region encoding functions for respiratory nitrate reduction. We found the highest amount of dnrE transcripts in aerobically nitrate-challenged cells. The gene was transcribed from two promoters, P1 and P2, of which promoter P1 was under the control of the nitrate response regulator NarL. The multiplicity of FNR factors in P. stutzeri underlines the versatility of the FNR scaffold to serve for transcriptional regulation directed at anaerobic or nitrate-activated metabolic processes.

Amino Acid Sequence↗
PubMed1998

Activities of the enzymes participating in purine and free-radical metabolism in cancerous human colorectal tissues.

Activities of adenosine deaminase, 5'-nucleotidase, xanthine oxidase, superoxide dismutase, glutathione peroxidase and catalase enzymes were measured in cancerous and non-cancerous adjacent colorectal tissues from 10 patients. Activities of DNA turn-over enzymes (ADA, 5'NT and XO) were found increased and those of free-radical metabolizing enzymes (SOD, GSH-Px and CAT) decreased in cancerous tissues compared with those of non-cancerous adjacent ones. Malondialdehyde (MDA) concentrations in cancerous tissues were also found higher than those of non-cancerous tissues, which indicated accelerated lipid peroxidation in the cancerous tissues. In the correlation analysis, disordered enzymatical relations were observed between the enzymes of both metabolic pathways. Results suggest that activities of purine metabolizing enzymes increase to cope with accelerated purine metabolism in cancerous tissues and, enzymatic antioxidant defense potential of cancerous tissues decreases due to carcinogenic processes in the tissues. Reduced antioxidant defense system makes the cancerous tissue more vulnerable to toxic effects of some free-radical species.

5'-Nucleotidase↗
PubMed2006

Sequential enzymatic reactions and stability of biomolecules immobilized onto phospholipid polymer nanoparticles.

Polymer nanoparticles for sequential enzymatic reactions were prepared by combining a phospholipid polymer shell with a polystyrene core. The active ester groups for the bioconjugation and phospholipid polar groups were incorporated into the phospholipid polymer backbone using a novel active ester monomer and 2-methacryloyloxyethyl phosphorylcholine. For the sequential enzymatic reactions, acetylcholinesterase, choline oxidase, and horseradish peroxidase-labeled IgG were immobilized onto the nanoparticles. As substrates, acetylcholine chloride, choline chloride, and tetramethylbenzidine were added to the nanoparticle suspension, the acetylcholine chloride was converted to choline chloride, the choline chloride was oxidized by choline oxidase, and hydrogen peroxide was then formed as an enzymatic degradation product. The hydrogen peroxide was used for the next enzymatic reaction (oxidized by peroxidase) with tetramethylbenzidine. The sequential enzymatic reactions on the nanoparticles via degradation products (hydrogen peroxide) were significantly higher than that of the enzyme mixture. This result indicated that the diffusion pathway of the enzymatic products and the localization of the immobilized enzyme were important for these reactions. These nanoparticles were capable of facilitating sequential enzymatic reactions.

Acetylcholinesterase↗
PubMed1988

Ligninolytic enzymes of the white-rot fungus Phlebia radiata.

One oxidase (EC 1.10.3.2) and three lignin peroxidases (EC 1.11.1.-) were purified from the culture liquid of the white-rot fungus Phlebia radiata Fr. All the enzymes were glycoproteins. The oxidase had Mr 64,000 and the lignin peroxidases I, II and III had Mr values 42,000, 45,000 and 44,000 respectively. The lignin peroxidases were found to share common antigenic determinants: lignin peroxidases II and III were serologically indistinguishable and lignin peroxidase I was related but distinguishable. The oxidase did not share any immunological properties with the lignin peroxidases. Lignin peroxidases of Phlebia contain protoporphyrin IX as a prosthetic group. In the presence of H2O2 and an electron donor, veratryl alcohol, lignin peroxidases exhibit spectral shifts analogous to those of animal catalase (EC 1.11.1.6). Phlebia enzymes show optimal activity at pH 3-4.5 at 40 degrees C and are stable in the pH range 5-6. They modify Kraft lignin and phenolic compounds containing hydroxy and methoxy groups.

Benzyl Alcohols↗
PubMed2005

Involvement of phospholipid, biomembrane integrity, and NO peroxidase activity in the NO catabolism by cytochrome c oxidase.

The physiological regulation of mitochondrial respiration by NO has been reported to result from the reversible binding of NO to the two-electron reduced binuclear center (Fe(2+)(a3)-Cu(1+)(B)) of cytochrome c oxidase (CcO). Although the role of CcO and its derived catalytic intermediates in the catabolism of NO has been documented, little has been established for the enzyme in its fully oxidized state (Fe(3+)(a3)-Cu(2+)(B)). We report: (1) CcO, in its fully oxidized state, represents the major component of the mitochondrial electron transport chain for NO consumption as controlled by the binding of NO to its binuclear center. Phospholipid enhances NO consumption by fully oxidized CcO, whereas the consumption of NO is slowed down by membrane structure and membrane potential when CcO is embedded in the phospholipid bilayer. (2) In the presence of H(2)O(2), CcO was shown to serve as a mitochondria-derived NO peroxidase. A CcO-derived protein radical intermediate was induced and involved in the modulation of NO catabolism.

Animals↗
PubMed1997

Two Distinct Sources of Elicited Reactive Oxygen Species in Tobacco Epidermal Cells.

Reactive oxygen species (ROS) play a prominent role in early and later stages of the plant pathogenesis response, putatively acting as both cellular signaling molecules and direct antipathogen agents. A single-cell assay, based on the fluorescent probe dichlorofluorescein, was used to scrutinize the generation and movement of ROS in tobacco epidermal tissue. ROS, generated within cells, quickly moved apoplastically as H2O2 into neighboring cells. Two classes of rapidly elicited intracellular ROS, originating from distinct sources, were distinguished. Cryptogein, the fungal elicitor from Phytophthora cryptogea, induced ROS from a flavin-containing oxidase source. ROS accumulation could be inhibited by a number of pharmacological agents, suggesting induction through an active signal transduction pathway. The insensitivity of the increase in ROS to the external addition of enzymes that dissipate ROS suggests that this oxidative increase is primarily intracellular. In contrast, amines and polyamines, compounds that form during wounding and pathogenesis, induced ROS at an apoplastic site from peroxidase- or amine oxidase-type enzyme(s). Salicylic acid, a putative inhibitor of cellular catalases and peroxidases, did not induce cellular ROS, as measured by dichlorofluorescein fluorescence. The physiological relevance of ROS-generated signals was indicated by the rapid alteration of the epidermal cell glutathione pool and the cellular redox state. In addition, induction of ROS by all elicitors was correlated with subsequent cell death.

Journal Article↗
PubMedDate not supplied

[Conjugation resistance to Fusarium graminearum Schwabe with multiple molecular forms of some enzymes in winter wheat].

Electrophoretic spectra of multiple molecular forms of peroxidase (EC 1.11.1.7), superoxide dismutase (EC 1.15.1.1), phenol oxidase (EC 1.10.3.1), and cytochrome oxidase (EC 1.9.3.1) in seedlings of two aegilops species and eleven genotypes of bread winter wheat differing in the level of their resistance to Fusarium infection are presented. Several izoforms of peroxidase, phenol oxidase, and superoxide dismutase correlate with the level of resistance to Fusarium. Infection of plants with the pathogen enhances expressiveness of some multiple forms of enzymes. Such response to infection in less pronounced in the sensitive genotypes as compared with that in the resistant ones.

Electron Transport Complex IV↗
PubMed1999

Industrial dye decolorization by laccases from ligninolytic fungi.

White-rot fungi were studied for the decolorization of 23 industrial dyes. Laccase, manganese peroxidase, lignin peroxidase, and aryl alcohol oxidase activities were determined in crude extracts from solid-state cultures of 16 different fungal strains grown on whole oats. All Pleurotus ostreatus strains exhibited high laccase and manganese peroxidase activity, but highest laccase volumetric activity was found in Trametes hispida. Solid-state culture on whole oats showed higher laccase and manganese peroxidase activities compared with growth in a complex liquid medium. Only laccase activity correlated with the decolorization activity of the crude extracts. Two laccase isoenzymes from Trametes hispida were purified, and their decolorization activity was characterized.

Alcohol Oxidoreductases↗
PubMed2005

Induction of resistance in host against the infection of leaf blight pathogen (Alternaria palandui) in onion (Allium cepa var aggregatum).

The Pseudomonas fluorescens isolate Pfl was found to inhibit the growth of pathogen Alternaria palandui, in vitro. In the present study, foliar application of a talc-based formulation of Pfl significantly reduced the incidence of leaf blight of onion, caused by A. palandui. Induction of defense-related proteins viz., chitinase, beta-1,3 glucanase, peroxidase (PO) and polyphenol oxidase (PPO) by application of Pfl, was studied against A. palandui infection in resistant (IHR 56) and susceptible (MDUI) onion cultivars. Chitinase in both cultivars, with or without challenge-inoculation of A. palandui revealed changes in the isoform pattern. The Native-PAGE of PO showed induction of PO2 isoform in both the cultivars, in response to inoculation of pathogen. Isoform analysis of PPO also exhibited induction in the Pfl-treated plants challenged with pathogen. Similarly, the activity of beta-1,3-glucanase was greatly induced in Pfl-treated plants, challenged with pathogen as compared to controls. Thus, the P. fluorescens-treated plants showed significant increase in the levels of the defense enzymes, in comparison to the plants challenged with the pathogen.

Catechol Oxidase↗
PubMed1988

The two terminal oxidases of the aerobic respiratory chain of Escherichia coli each yield water and not peroxide as a final product.

The aerobic respiratory chain of Escherichia coli contains two terminal oxidases, the cytochrome d complex and the cytochrome o complex. Each of these enzymes catalyzes the oxidation of ubiquinol-8 within the cytoplasmic membrane and reduces molecular oxygen. The purpose of this work is to experimentally verify that each of the terminal oxidases yields water as a product with no significant amount of hydrogen peroxide. This was accomplished by preparing membranes which were washed so as to eliminate membrane-associated catalase and peroxidase activities. The NADH oxidase activity of the membrane-bound respiratory chain was measured by monitoring the rates of both NADH and oxygen utilization. This was performed using membranes from strains in which either cytochrome o or cytochrome d were absent. Results using each strain showed two NADH utilized per oxygen, indicating a four-electron reduction of oxygen to water.

Aerobiosis↗