Catalases decomposition

Enzyme Decay. Moffett and Zafiriou (I) differentiated catalase- and peroxidase-mediated decay in coastal (marine) waters by using lsO-labeled H202 and 02, and by determining the labeled end products. Equation 13 shows that the products of catalase decomposition are H20 and 02. In contrast, peroxidase decomposition results in the formation of H20 without 02. From the measurement of the relative amount of labeled products it is possible to determine the contribution of both enzymes in the decay of the H202. In the coastal water, 65-80% of the decomposition was attributed to catalase and the rest to peroxidase (I). These studies are the first to use this technique. The approach should be extended to freshwater ecosystems to see if the same pattern would be found. 

Both in structure and in functions, catalase is akin to peroxidase. Catalase is the most effective among all known catalysts for the decomposition of hydrogen peroxide (k = 10 s ) and it displays, moreover, a peroxidase activity. The catalase molecule with a molecular mass of 225,000 is comprised of four subunits, each of which contains a hematin group. Hydrogen peroxide forms three compounds with catalase. Decomposition of H2O2 or ROOH occurs as a result of interaction between compound I of the catalase and the second substrate molecule. Not only hydroperoxides but other hydrogen donors, for instance, ethanol, are capable of reacting with compound I. 

Haber, F., and Weiss, J., 1934, The catalase decomposition of hydrogen peroxide by iron salts, Proc. R. Soc. London Ser. A 147 332-351. 

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

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... 

As an example, we mention the enzyme catalase, which catalyzes the decomposition of H2O2 to H2O and O2 at a turnover number of kcat = 10 and a high specificity constant of kcat/f M = 4 x 10 mol s . Such activities are orders of magnitude higher than those of heterogeneous catalysts. 

Concerning the mode of formation of ES, we prefer the concept that the substrate in a monolayer is chemisorbed to the active center of the enzyme protein, just as the experimental evidence pertaining to surface catalysis by inorganic catalysts indicates that in these reactions chemisorbed, not physically adsorbed, reactants are involved. Such a concept is supported by the demonstration of spectroscopically defined unstable intermediate compounds between enzyme and substrate in the decomposition by catalase of ethyl hydroperoxide,11 and in the interaction between peroxidase and hydrogen peroxide.18 Recently Chance18 determined by direct photoelectric measurements the dissociation con-... 

In the Thought Lah above, you may have included the enzyme catalase in your brainstormed list. Catalase in your blood is responsible for the fizzing you see when you use a dilute hydrogen peroxide solution to disinfect a cut. When dilute hydrogen peroxide is poured on a cut, it decomposes to oxygen gas and water. The decomposition reaction is catalyzed by catalase. 

In Investigation 6-B, you will write a detailed procedure to determine the rate law for the catalyzed decomposition of hydrogen peroxide. Instead of using catalase to catalyze the reaction, you will use an inorganic catalyst. 

The Bombardier beetle possesses, at the end of its abdomen, a combustion chamber that contains a hydroqui-none and hydrogen peroxide. When a predator approaches, the cells in the walls of the combustion chamber secrete two enzymes, catalase and peroxidase. Catalase causes decomposition of hydrogen peroxide to produce oxygen peroxidase catalyses the oxidation of the hydroquinone to produce a quinone. 

Fig. 2. The Bonnichsen, Chance, and Theorell 34) mechanism for the dismutation of hydrogen peroxide by catalase. (A) The simple ping-pong mechanism (ferric-peroxide compound (ycle) involves only the successive formation and decomposition of the compound 1 intermediate by two successive molecules of H2O2. (B) Reversible ES(Fe -H202) and ternary (compound I-H2O2]) complexes are added to the mechanism in A.

Manganese is used by nature to catalyze a number of important biological reactions that include the dismutation of superoxide radicals, the decomposition of hydrogen peroxide, and the oxidation of water to dioxygen. The dinuclear manganese centers that occur in Lactobacillus plantar-aum catalase and Thermus thermophilus catalase have attracted considerable attention and many model compounds have now been synthesized that attempt to mimic aspects of these biological systems.The catalases have at least four accessible oxidation states (Mn Mn , Mn°Mn , Mn" Mn", and Mn Mn ) it is believed that the Mn"Mn"/Mn"Mn" redox couple is effective in catalyzing the disproportionation of water. 

DHAP can be prepared by oxidation of L-glycerol-3-phosphate (L- G3P) catalyzed by glycerophosphate oxidase, coupled with hydrogen peroxide decomposition in the presence of catalase (Scheme 4.5) [14]. More recently, this synthetic route has... 

Catalase (fungal) HA inhibits decomposition of H2O2 with IC50 values ranging from 25 to 260 nM 56... 

Influence of catalase activity and electrical conductivity. Parallel to the determination of the oxygen activity. Beck and co-workers 38> investigated the activity for the decomposition of hydrogen peroxide by various chelates. In each case, 1 mg of freshly precipitated pigment was added to 1% hydrogen peroxide solution and the velocity of oxygen evolution was determined volumetri-cally. The results summarized in Table 5 show no correlation between electro-catalytic activity and catalase activity. 

Catalase A haem-based enzyme which catalyzes the decomposition of hydrogen peroxide into oxygen and water. It is found e.g. in peroxisome located in the liver. 

Catalase - piSINFECTANTSAND ANTISEPTICS] (Vol 8) - pGGS] (Vol 8) -genes for [GENETIC ENGINEERING - MICROBES] (Vol 12) -iron in [MINERAL NUTRIENTS] (Vol 16) -iron compounds [IRON COMPOUNDS] (Vol 14) -role in H202 decomposition [HYDROGEN PEROXIDE] (Vol 13) -use in biosensors [BIOSENSORS] (Vol 4)... 

Biological Decay. The two major enzyme systems that are used to control intracellular H202 concentrations in organisms are catalases and peroxidases (47). The different overall reactions for H202 decomposition mediated by these two enzyme systems can be illustrated as follows for catalase ... 

Another approach uses the coupling reaction of p-anisidine. In the presence of H202 and peroxidase (16), an oxidation product that contains two aromatic rings, benzoquinone-4-methoxyaniline, is formed stoichiometri-cally (92). Equations 14-16 indicate that an electron donor or hydrogen donor is required for peroxidase-mediated decomposition of H202. In two natural waters and one soil suspension, peroxidatic activity was identified by the stoichiometric removal of p-anisidine by the addition of H202 (in the dark) (16). This procedure provides an independent corroboration of the results obtained by Moffett and Zafiriou (1). However, this method does not quantify the relative importance of peroxidases versus catalases in the decomposition of H202. 

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