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Peroxidase
From Wikipedia, the free encyclopedia
Peroxidases (EC number 1.11.1.x) are a large family of enzymes. A majority of peroxidase protein sequences can be found in the PeroxiBase database. Peroxidases typically catalyze a reaction of the form:
- ROOR' + electron donor (2 e-) + 2H+ → ROH + R'OH
For many of these enzymes the optimal substrate is hydrogen peroxide, but others are more active with organic hydroperoxides such as lipid peroxides. Peroxidases can contain a heme cofactor in their active sites, or redox-active cysteine or selenocysteine residues.
The nature of the electron donor is very dependent on the structure of the enzyme.
- For example, horseradish peroxidase can use a variety of organic compounds as electron donors and acceptors. Horseradish peroxidase has an accessible active site and many compounds can reach the site of the reaction.
- For an enzyme such as cytochrome c peroxidase, the compounds that donate electrons are very specific, because there is a very closed active site.
While the exact mechanisms have yet to be elucidated, peroxidases are known to play a part in increasing a plant's defenses against pathogens.[1] Peroxidases are sometimes used as histological marker. Cytochrome c peroxidase is used as a soluble, easily purified model for cytochrome c oxidase.
Glutathione peroxidase is a peroxidase found in humans, which contains selenocysteine. It uses glutathione as an electron donor and is active with both hydrogen peroxide and organic hydroperoxide substrates.
Amyloid beta, when bound to heme has been shown to have peroxidase activity.[2]
- ^ Karthikeyan M et al (2005 Dec). "Induction of resistance in host against the infection of leaf blight pathogen (Alternaria palandui) in onion (Allium cepa var aggregatum).". Indian J Biochem Biophys 42 (6): 371-7. PMID 16955738.
- ^ Hani Atamna, Kathleen Boyle (21 Feb 2006). "Amyloid-{beta} peptide binds with heme to form a peroxidase: Relationship to the cytopathologies of Alzheimer's disease". Proceedings of the National Academy of Science 103 (9): 3381 - 3386. doi:10.1073/pnas.0600134103.
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| Topics | Active site - Allosteric regulation - Binding site - Catalytically perfect enzyme - Coenzyme - Cofactor - Cooperativity - EC number Enzyme catalysis - Enzyme inhibitor - Enzyme kinetics - Lineweaver-Burk plot - Michaelis-Menten kinetics - List of enzymes |
| Types | EC1 Oxidoreductases/list - EC2 Transferases/list - EC3 Hydrolases/list - EC4 Lyases/list - EC5 Isomerases/list - EC6 Ligases/list |