Disproportionation of hydrogen peroxid

Catalase is a heme protein belonging to the class of oxidoreductases with ferripro-toporphyrin-IX at the redox center, and it catalyzes the disproportionation of hydrogen peroxide into oxygen and water without the formation of free radicals. 

Olas and Wachowicz (2002) investigated the effects of tranx-resveratrol and vitamin C on oxidative stress in blood platelets. The level of 02 in control blood platelets and platelets incubated with resveratrol or vitamin C was recorded using a chemiluminescence method. On the other hand, Oh and others (2006) reported the x02 quenching activities of various freshly squeezed fruit and vegetable juices by measuring their inhibitory effects on the rubrene oxidation induced by x02 from disproportionation of hydrogen peroxide by sodium molybdate in a microemulsion system. 

Rate Constants (in M 1s 1) and Equilibrium Constants and Activation Parameters for Iron(III)-TAML Catalyzed Disproportionation of Hydrogen Peroxide (Eq. (17)) at 25°C and 0.1 M Phosphate... 

Bacterial SODs typically contain either nonheme iron (FeSODs) or manganese (MnSODs) at their active sites, although bacterial copper/zinc and nickel SODs are also known (Imlay and Imlay 1996 Chung et al. 1999). Catalases are usually heme-containing enzymes that catalyze disproportionation of hydrogen peroxide to water and molecular oxygen (Eq. 10.2) (Zamocky and Koller 1999 Loewen et al. 2000). 

Use standard reduction potentials to calculate the equilibrium constant at 25°C for disproportionation of hydrogen peroxide ... 

Dipeptides complex in a trident fashion to form oxoperoxodipeptido products. The rate of complexation by these ligands is quite slow. Even the vanadium-catalyzed disproportionation of hydrogen peroxide occurs quickly when compared to the rate of complexation by dipeptides. The formation of the dipeptide complex is interesting, in the sense that the ligand is tridentate, and complex formation involves loss of a... 

Complex 29 catalyzes the disproportionation of hydrogen peroxide to oxygen and water (48). In the absence of readily oxidizable substrates, it degrades. In the presence of olefins, however, it catalyzes the formation of epoxides. This catalysis was demonstrated for cyclohexene (1.6 turnovers), styrene (3.2 turnovers), and ds-stilbene (2.5 turnovers). The formation of the epoxides is not exclusive, because allylic oxidation... 

Mn Catalase. The majority of known catalases contain a heme prosthetic group to catalyze the disproportionation of hydrogen peroxide. These enzymes are long established (e.g., the beef liver catalase was crystallized in 1937 (13)) and are believed to protect respiring cells... 

The V-BrPO-catalyzed oxidation of bromide by hydrogen peroxide is the first step in a series of reactions that results in brominated organic products or the halide-assisted disproportionation of hydrogen peroxide. As studies continue on both the enzymatic and model systems, we can make several comments. The ability to catalyze this reaction seems to be a fairly general property of vanadium(V) complexes with an available coordination site in the equatorial plane in which to bind peroxide. The oxidation rates of the model complexes, with respect to the enzyme, raise the question of what microscopic differences give rise to the high... 

Peroxidase and catalase enzymes catalyze oxidations by hydrogen peroxide and the disproportionation of hydrogen peroxide into dioxygen and water (equations 36 and 37). The two classes of... 

The catalases catalyze the disproportionation of hydrogen peroxide (equations). Most catalases contain the iron-protoporphyrin IX prosthetic group see Iron Heme Proteins, Peroxidases, Catalases Catalase-peroxidases). However, some bacteria are able to synthesize catalases that are not inhibited even by millimolar concentrations of azide and cyanide, suggesting that some catalases are nonheme enzymes it is now known that these enzymes possess a dinuclear Mn active site. 

Equation (26) can be easily transformed to Eq. (25) by disproportionation of hydrogen peroxide. It is quite interesting that the products of reaction (25) have been labeled as carbon monoxide detonating gas more than 70 years ago 24). This emphasizes also the analogy of splitting water (Eq. 7) and carbon dioxide (Eq. 25). 

The disproportionation of hydrogen peroxide is thermodynamically favourable however, rapid reaction requires a two-electron catalyst. For haem catalases, this is achieved by cycling between Fe and Fe porphyrin... 

Autoregeneration of oxidases with concomitant catalase-catalyzed disproportionation of hydrogen peroxide is a simple and effective regeneration method (Fig. 16.2-23) it is quite commonly used with oxidase reactions. 

The above reaction is also catalysed by several transition metal ions and metal complexes provided the coordination sphere is accessible for H Oj and/or HOj. In our laboratory catalytic activity of transition metal ions and metal complexes supported on various zirconium based inorganic ion exchangers has been studied in detail for the disproportionation of hydrogen peroxide ". 

In the present endeavour a titanium based inorganic ion exchanger titanium tungstate (TiW) has been used as a support onto which [CuCNHjlJ has been anchored. The support (TiW) and the catalyst (CuT-TiW) have been characterised for elemental analysis, t.g.a., ft.i.r., e.s.r., reflectance spectroscopy and surface area measurements. The catalytic activity has been studied for the disproportionation of hydrogen peroxide at different temperatures, different concentrations of hydrogen peroxide and different amounts of the catalyst. 

Catalase and peroxidase are heme enzymes that catalyze reactions of hydrogen peroxide.In catalase, the enzymatic reaction is the disproportionation of hydrogen peroxide (Reaction 5.82) and the function of the enzyme appears to be prevention of any buildup of that potentially dangerous oxidant (see the discussion of dioxygen toxicity in Section III). 

Scheme 8. A proposed mechanism for the disproportionation of hydrogen peroxide by manganese catalase, based on the mechanism proposed by Penner-Hahn in 1992, and the T. thermophilus catalase crystal structure. [Adapted with permission from (24). Copyright 1992 WILEY-VCH Verlag.]...

Okawa and co-workers have published several papers in recent years on binuclear catalase mimics based on the pentadentate or sep-tadentate binucleating ligands, an example of which is shown in Scheme 21 (441, 442). These ligands have been used to prepare a variety of binuclear Mn" complexes. Their ability to catalyze the dis-porportionation of hydrogen peroxide varies, but is generally low, on the order of 0.79 s 1. A functional scheme for the disproportionation of hydrogen peroxide has been proposed for these complexes that invokes a MnIV=0 intermediate (Scheme 21). 

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