Catalases hydrogen peroxide

By application of EMMA Regehr and Regnier developed several assays for enzymes that produce (galactose oxidase and glucose oxidase) or consume (catalase) hydrogen peroxide. Unlabeled enzymes were determined in the femto-mole mass range, while detection limits of less than 10,000 molecules were reported for catalase [101]. 

Sulfonamides (c)P Or by inhibiting catalase, hydrogen peroxide accumulating... 

In the presence of the enzyme catalase, hydrogen peroxide is rapidly converted to water and oxygen, which... 

Wang and colleagues studied file functionalization of composite nanofibers of poly(acrylonitrile-co-acrylic acid) [P(AN-AA)] and multiwalled carbon nanotubes (MWCNTs) by attaching catalase (hydrogen peroxide oxido-reductase from bovine liver) onto the carbon nanotube surface. The activity of the catalase was reported to increase by about 42% with increasing MWCNT content in the composite nanofiber and was attributed to promotion of electron transfer via charge-transfer complexes formed by carbon nanotubes (Wang, Z.-G., et al. 2006). 

Fig. 9. The kinetics of H2O2 disappearance and of the catalase-hydrogen peroxide complex (Expt. 650f).

Catalase living tissues of plants and animals hydrogen peroxide HjO and inactive molecular O, 70... 

Several other biosensors have been developed usiag this oxygen-quenched fluorescence approach. Target species iaclude ethanol [64-17-5] hydrogen peroxide [7722-84-17, H2O2, lactate, and xanthine [69-89-6] C H4N402, usiag alcohol oxidase, catalase [9001-05-2] lactate oxidase, and xanthine oxidase, respectively. An additional technique for biocatalytic biosensors iavolves the firefly chemiluminescent reaction (17) ... 

In another method, hydrogen peroxide can be added to the Hquid egg white after it has been heated at 52°C for a holding time of 1 minute (18) to inactivate the natural catalase and to allow the hydrogen peroxide to react against bacteria. Hoi ding time after addition of the hydrogen peroxide is 2.5 min... 

Decomposition of hydrogen peroxide (H2O2) in aqueous solution with catalase. 

The hydrogen peroxide produced in the glucose oxidase catalyzed reaction has an antibacterial action. If the presence of hydrogen peroxide is undesirable in the product, catalase is added to remove the peroxide. 

Catalase An enzyme that catalyses the breakdown of hydrogen peroxide to water and oxygen. 

One of the important consequences of neuronal stimulation is increased neuronal aerobic metabolism which produces reactive oxygen species (ROS). ROS can oxidize several biomoiecules (carbohydrates, DNA, lipids, and proteins). Thus, even oxygen, which is essential for aerobic life, may be potentially toxic to cells. Addition of one electron to molecular oxygen (O,) generates a free radical [O2)) the superoxide anion. This is converted through activation of an enzyme, superoxide dismurase, to hydrogen peroxide (H-iO,), which is, in turn, the source of the hydroxyl radical (OH). Usually catalase... 

In blood or tissues, this reaction is catalyzed by an enzyme called catalase (Figure 11.13). When 3% hydrogen peroxide is used to treat a fresh cut or wound, oxygen gas is given off rapidly. The function of catalase in the body is to prevent the build-up of hydrogen peroxide, a powerful oxidizing agent. 

Quantitative tests for catalase activity find their greatest usefulness in examination of finished product. For this purpose gasometric methods (36) or chemical methods based upon measurement of residual hydrogen peroxide (2) may be used. In the use of these quantitative methods it might be well to observe the precaution of removing the skins. 

In this reaction, hydrogen peroxide is produced which is toxic to cells and has to be removed quickly and efficiently. This is carried out by the enzyme catalase. The C°wrafion equation also indicates the need for molecular oxygen and the fermentation process needs a continuous supply of air. 

Heme (C34H3204N4Fe) represents an iron-porphyrin complex that has a protoporphyrin nucleus. Many important proteins contain heme as a prosthetic group. Hemoglobin is the quantitatively most important hemoprotein. Others are cytochromes (present in the mitochondria and the endoplasmic reticulum), catalase and peroxidase (that react with hydrogen peroxide), soluble guanylyl cyclase (that converts guanosine triphosphate, GTP, to the signaling molecule 3, 5 -cyclic GMP) and NO synthases. 

Catalase is an important enzyme in cells because hydrogen peroxide is a by-product of metabolism and can poison the cell unless it is decomposed quickly. Hydrogen peroxide is also produced by cells in the immune system, and catalase removes the excess. 

Catalase is a hver enzyme that uses hydrogen peroxide to oxidize other substances. In vivo, the catalase system does not play a significant role in ethanol metabolism, probably because the quantities of hydrogen peroxide available are insufficient for ethanol metabolism. 

Catalase Uses Hydrogen Peroxide as Electron Donor Electron Acceptor... 

Under most conditions in vivo, the peroxidase activity of catalase seems to be favored. Catalase is found in blood, bone marrow, mucous membranes, kidney, and fiver. Its function is assumed to be the destruction of hydrogen peroxide formed by the action of oxidases. 

Superoxide is formed (reaction 1) in the red blood cell by the auto-oxidation of hemoglobin to methemo-globin (approximately 3% of hemoglobin in human red blood cells has been calculated to auto-oxidize per day) in other tissues, it is formed by the action of enzymes such as cytochrome P450 reductase and xanthine oxidase. When stimulated by contact with bacteria, neutrophils exhibit a respiratory burst (see below) and produce superoxide in a reaction catalyzed by NADPH oxidase (reaction 2). Superoxide spontaneously dismu-tates to form H2O2 and O2 however, the rate of this same reaction is speeded up tremendously by the action of the enzyme superoxide dismutase (reaction 3). Hydrogen peroxide is subject to a number of fates. The enzyme catalase, present in many types of cells, converts... 

Enzymes are exceptionally efficient catalytic proteins which increase the speed of a chemical reaction without themselves undergoing a permanent change. Under optimal conditions, most enzymatic reactions proceed from 10 to 10 times more rapidly than the corresponding non-enzymatic reactions. For example, one molecule of catalase, the enzyme which converts hydrogen peroxide into water and atomic oxygen, is able to deal with approximately 5 million molecules of H2O0 per minute. 

Enzymes are nature s catalysts. For the moment it is sufficient to consider an enzyme as a large protein, the structure of which results in a very shape-specific active site (Fig. 1.3). Flaving shapes that are optimally suited to guide reactant molecules (usually referred to as substrates) in the optimum configuration for reaction, enzymes are highly specific and efficient catalysts. For example, the enzyme catalase catalyzes the decomposition of hydrogen peroxide into water and oxygen... 

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