Protein catalase

Large molecular weight proteins (catalase, /1-galac-tosidase, BSA, hemoglobin) AOT/isooctane Extraction and purification [99]... 

This is accelerated by the iron heme protein catalase, a particularly efficient enzyme with one of the highest turnover numbers of all known enzymes (at 4x 107 molecules per second). This high rate reflects the important role for the enzyme, and its capacity for detoxifying hydrogen peroxide. 

Balestrieri 1978 2 Aromatic aminoacids in proteins (catalase, RNase, lysozyme) 305... 

Although, salen Mn complexes for therapeutic use were originally conceived as SOD mimetics, it soon became clear that EUK-8 also exhibited catalase activity, the ability to metabolize hydrogen peroxide (75). The catalase activity of EUK-8 was not unexpected, since Mn porphyrins had been studied as catalase models by the Meunier laboratory (16) and, like the porphyrins, salen ligands form stable complexes with Mn(III) (6). As described previously (77), similar to that of mammalian heme-iron based catalases (78), the catalase activity of salen Mn complexes is not saturable with respect to hydrogen peroxide. As has been reported for protein catalases (18), salen Mn complexes exhibit peroxidase activity, in the presence of an electron donor substrate, as an alternative to a catalatic pathway. This supports the analogy between the behavior of these mimetics and that of catalase enzymes, and is consistent with the following mechanistic scheme (76,17) ... 

A marked difference between the peroxidase activity of salen Mn complexes and protein catalases is the broader substrate-specificity of the synthetic complexes, a difference likely due to steiic factors, vine tetrameric catalase recognizes primarily short-chain alcohols, while the dissociated subunits are able to oxidize larger substrates (20,18). For convenience, the peroxidase activity of salen Mn complexes can be monitored with colorimetric substrates not recognized by protein catalases (27, 77). 

An acetylcholine receptor may be immobilized in the place of the antibody on the ISFET. In the presence of the positively-charged acetylcholine, the potential difference between the sensing element and that of a reference ISFET (REFET) without a receptor changes in the same direction, indicating that the acetylcholine is strongly bound to its receptor. This is not the case for other proteins (catalase or BS A) when they are fixed in the place of the acetylcholine receptor. 

Schiff base fonnation, photochemistry, protein partitioning, catalysis by chymotrypsin, lipase, peroxidase, phosphatase, catalase and alcohol dehydrogenase. 

Two classes of antioxidants are known the low-molecular weight compounds (tocopherols, ascorbate, -carotene, glutathione, uric acid and etc.) and the proteins (albumin, transferrin, caeruloplasmin, ferritin, etc.) including antioxidant enzymes (e.g. superoxide dismutase, catalase, glutathione peroxidase). 

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... 

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. 

By adding 1-alkanols to AOT-based w/o microemulsions, some proteins (ribonucle-ase, lysozyme, alpha-chymotrypsin, pepsin, bovine serum albumin, and catalase) are readily expelled, while the major part of the surfactant remained in solution [171]. 

As a result of the micellar environment, enzymes and proteins acquire novel conformational and/or dynamic properties, which has led to an interesting research perspective from both the biophysical and the biotechnological points of view [173-175], From the comparison of some properties of catalase and horseradish peroxidase solubilized in wa-ter/AOT/n-heptane microemulsions with those in an aqueous solution of AOT it was ascertained that the secondary structure of catalase significantly changes in the presence of an aqueous micellar solution of AOT, whereas in AOT/n-heptane reverse micelles it does not change. On the other hand, AOT has no effect on horseradish peroxidase in aqueous solution, whereas slight changes in the secondary structure of horseradish peroxidase in AOT/n-heptane reverse micelles occur [176],... 

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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