Search results for "OXIDASE"

Impact of Reactive Oxygen Species on the Expression of Adhesion Molecules in Vivo

2008

Many non-surgical tumor treatments induce reactive oxygen species (ROS) which result in cell damage. This study investigated the impact of ROS induction on the expression of adhesion molecules and whether alpha-tocopherol pre-treatment could have a protective effect. Experimental rat DS-sarcomas were treated with a combination of localized 44 degrees C-hyperthermia, inspiratory hyperoxia and xanthine oxidase which together lead to a pronounced ROS induction. Further animals were pre-treated with alpha-tocopherol. The in vivo expression of E- and N-cadherin, alpha-catenin, integrins alpha v, beta 3 and beta 5 as well as of the integrin dimer alpha v beta 3 was assessed by flow cytometry. The…

Laccases: structure, reactions, distribution

2004

Laccases (EC 1.10.3.2, p-diphenol: dioxygen oxidoreductases) are multi-copper proteins that use molecular oxygen to oxidize various aromatic and non-aromatic compounds by a radical-catalyzed reaction mechanism. The enzymes are involved in the pathogenicity, immunity and morphogenesis of organisms and in the metabolic turnover of complex organic substances such as lignin or humic matter. Owing to their high non-specific oxidation capacity, laccases are useful biocatalysts for diverse biotechnological applications. Until recently, laccases were only found in eukaryotes (fungi, higher plants, insects), but now there is strong evidence for their widespread distribution in prokaryotes and the fi…

Functional Enzyme Mimics for Oxidative Halogenation Reactions that Combat Biofilm Formation

2017

Transition-metal oxide nanoparticles and molecular coordination compounds are highlighted as functional mimics of halogenating enzymes. These enzymes are involved in halometabolite biosynthesis. Their activity is based upon the formation of hypohalous acids from halides and hydrogen peroxide or oxygen, which form bioactive secondary metabolites of microbial origin with strong antibacterial and antifungal activities in follow-up reactions. Therefore, enzyme mimics and halogenating enzymes may be valuable tools to combat biofilm formation. Here, halogenating enzyme models are briefly described, enzyme mimics are classified according to their catalytic functions, and current knowledge about th…

Tuneable Transient Thermogels Mediated by a pH- and Redox-Regulated Supramolecular Polymerization.

2017

A multistimuli-responsive transient supramolecular polymerization of β-sheet-encoded dendritic peptide monomers in water is presented. The amphiphiles, which contain glutamic acid and methionine, undergo a glucose oxidase catalyzed, glucose-fueled transient hydrogelation in response to an interplay of pH and oxidation stimuli, promoted by the production of reactive oxygen species (ROS). Adjusting the enzyme and glucose concentration allows tuning of the assembly and the disassembly rates of the supramolecular polymers, which dictate the stiffness and transient stability of the hydrogels. The incorporation of triethylene glycol chains introduces thermoresponsive properties to the materials. …

Characterization of 1-aminocyclopropane-1-carboxylic acid oxidase from barley (Hordeum vulgare L.) seedlings and pine (Pinus sylvestris L.) needles

1999

Abstract Biochemical characteristics of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase extracted from barley ( Hordeum vulgare L.) leaves and pine ( Pinus sylvestris L.) needles were investigated. ACC oxidase from barley leaves was soluble while for complete recovery of ACC oxidase from pine needles addition of Triton X-100 to extraction medium was necessary. The enzyme required Fe 2+ , ascorbate and NaHCO 3 for maximum activity. A non-linear time course of ACC oxidase reaction indicated possible catalytic inactivation of the enzyme. The maximum activity was measured at pH 7.0–7.2 for ACC oxidase from both barley leaves and pine needles. The apparent K m for ACC was found to be 77 and …

Sildenafil protects human mammary epithelial cells against ROS production induced by estradiol

2010

Several studies suggest that xanthine dehydrogenase (XDH) and its oxidase form (XO) play an important role in various types of ischemic and vascular injuries. Recently, we have demonstrated that estradiol (E2) induces a significant decrease of the expression and activity of XDH and of its conversion to XO in human mammary epithelial cells. E2 is known to induce upregulation of eNOS gene expression in aortic endothelial cells. Because the XO-derived O2·- combines with ·NO to yield ONOO-, and considering that ONOO- converts XDH to XO, the resulting increase of XO activity and reactive oxygen species production would eventually lead to a further increase of ONOO- production, thus creating a vi…

Cavernolide

2000

Abstract The inhibitory effect of cavernolide, a novel C 21 terpene lactone isolated from the sponge Fasciospongia cavernosa , on PLA 2 and other enzyme activities involved in the inflammatory process was studied. Cavernolide inhibited human synovial sPLA 2 in a concentration-dependent manner with an IC 50 value of 8.8 μM. Besides, this compound decreased in the nanomolar range the myeloperoxidase degranulation process using different stimuli. Cavernolide also inhibited TNFα, NO and PGE 2 production in intact cell experiments. NO and PGE 2 reduction was the consequence of the inhibition on iNOS and COX-2 expression because it did not affect inducible nitric oxide synthase and cyclooxygenase…

Oxidative oligomerization of cyclodextrin-complexed bifunctional phenols catalyzed by horseradish peroxidase in water

2000

The HRP-catalyzed oligomerization of hydrophobic bifunctional phenols in water was realized by the use of 2,6-di-O-methylated β-cyclodextrin. The molecular weights of the resulting oligomers were in the same region as they were reached by conventional HRP-catalyzed oligomerizations in water/dioxane-mixtures. The polymerizable moieties, maleimide and methacrylamide, were not affected during the oligomerization process, as proofed by NMR, MALDI-TOF and FT-IR measurements. It was therefore possible to get soluble functionalized oligomers, which were crosslinked via radical copolymerization with suitable components (styrene, MMA) or heating.

Interplays between nitric oxide and reactive oxygen species in cryptogein signalling

2014

The cellular messenger nitric oxide (NO) has many functions in plants. In this study, we investigated its interplays with Reactive Oxygen Species (ROS) in the defense responses triggered by the elicitin cryptogein produced by the oomycete Phytophthora cryptogea. The production of NO induced by cryptogein in tobacco cell suspensions was partly regulated through a ROS-dependent pathway involving the NADPH oxidase NtRBOHD. In turn, NO down-regulated the level of H2O2 derived from NtRBOHD activity. Both NO and ROS synthesis appeared to be under the control of two redundant isoforms of histone deacetylases of type 2 acting as negative regulators of cell death. Occurrence of an interplay between …

2013

Re-canalization of cerebral vessels in ischemic stroke is pivotal to rescue dysfunctional brain areas that are exposed to moderate hypoxia within the penumbra from irreversible cell death. Goal of the present study was to evaluate the effect of moderate hypoxia followed by reoxygenation (MHR) on the evolution of reactive oxygen species (ROS) and blood-brain barrier (BBB) integrity in brain endothelial cells (BEC). BBB integrity was assessed in BEC in vitro and in microvessels of the guinea pig whole brain in situ preparation. Probes were exposed to MHR (2 hours 67-70 mmHg O2, 3 hours reoxygenation, BEC) or towards occlusion of the arteria cerebri media (MCAO) with or without subsequent repe…