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Haloperoxidase
Haloperoxidases are peroxidases that are able to mediate the oxidation of halides by hydrogen peroxide. Both halides and hydrogen peroxide are widely available in the environment. The Nernst equation shows that hydrogen peroxide can oxidize chloride (E°= 1.36 V), bromide (E°= 1.09 V) and iodide (E°= 0.536 V) from a thermodynamic perspective under natural conditions, i.e., a temperature range of about 0–30 °C and a pH ranging from about 3 (humic soil layer) to about 8 ( sea water). Fluoride (E°= 2.87 V) cannot be oxidized by hydrogen peroxide. Classification The table shows the classification of haloperoxidases according to the halides whose oxidation they are able to catalyze. The classification of these enzymes by substrate-usability does not necessarily indicate enzyme substrate ''preference.'' For example, although eosinophil peroxidase is ''able'' to oxidize chloride, it preferentially oxidizes bromide. The mammalian haloperoxidases myeloperoxidase (MPO), lacto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peroxidases
Peroxidases or peroxide reductases ( EC numberbr>1.11.1.x are a large group of enzymes which play a role in various biological processes. They are named after the fact that they commonly break up peroxides. Functionality Peroxidases typically catalyze a reaction of the form: :ROOR' + \overset + 2H+ -> ce + R'OH Optimal substrates 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 alternately 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. * On the other hand, for an enzyme such as cytochrome c peroxidase, the com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vanadium Bromoperoxidase
Vanadium bromoperoxidases are a kind of enzymes called haloperoxidases. Its primary function is to remove hydrogen peroxide which is produced during photosynthesis from in or around the cell. By producing hypobromous acid (HOBr) a secondary reaction with dissolved organic matter, what results is the bromination of organic compounds that are associated with the defense of the organism. These enzymes produce the bulk of natural organobromine compounds in the world. Vanadium bromoperoxidases are one of the few classes of enzymes that requires vanadium. The active site features a vanadium oxide center attached to the protein via one histidine side chain and a collection of hydrogen bonds to the oxide ligands. Occurrence and function Vanadium bromoperoxidases have been found in bacteria, fungi, marine macro algae ( seaweeds), and marine microalgae (diatoms) which produce brominated organic compounds. It has not been definitively identified as the bromoperoxidase of higher eukaryot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thiocyanate
Thiocyanate (also known as rhodanide) is the anion . It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Mercury(II) thiocyanate was formerly used in pyrotechnics. Thiocyanate is analogous to the cyanate ion, , wherein oxygen is replaced by sulfur. is one of the pseudohalides, due to the similarity of its reactions to that of halide ions. Thiocyanate used to be known as rhodanide (from a Greek word for rose) because of the red colour of its complexes with iron. Thiocyanate is produced by the reaction of elemental sulfur or thiosulfate with cyanide: : 8 CN- + S8 -> 8 SCN- : CN- + S2O3^2- -> SCN- + SO3^2- The second reaction is catalyzed by thiosulfate sulfurtransferase, a hepatic mitochondrial enzyme, and by other sulfur transferases, which together are responsible for around 80% of cyanide metabolism in the body. Biological chemistry of thiocyanate in medicine Thiocyanate is known to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eosinophil
Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells (WBCs) and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. Along with mast cells and basophils, they also control mechanisms associated with allergy and asthma. They are granulocytes that develop during hematopoiesis in the bone marrow before migrating into blood, after which they are terminally differentiated and do not multiply. They form about 2 to 3% of WBCs. These cells are eosinophilic or "acid-loving" due to their large acidophilic cytoplasmic granules, which show their affinity for acids by their affinity to coal tar dyes: Normally transparent, it is this affinity that causes them to appear brick-red after staining with eosin, a red dye, using the Romanowsky method. The staining is concentrated in small granules within the cellular cytoplasm, which contain many chemical mediators, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutrophil
Neutrophils (also known as neutrocytes or heterophils) are the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. They form an essential part of the innate immune system, with their functions varying in different animals. They are formed from stem cells in the bone marrow and differentiated into subpopulations of neutrophil-killers and neutrophil-cagers. They are short-lived and highly mobile, as they can enter parts of tissue where other cells/molecules cannot. Neutrophils may be subdivided into segmented neutrophils and banded neutrophils (or bands). They form part of the polymorphonuclear cells family (PMNs) together with basophils and eosinophils. The name ''neutrophil'' derives from staining characteristics on hematoxylin and eosin ( H&E) histological or cytological preparations. Whereas basophilic white blood cells stain dark blue and eosinophilic white blood cells stain bright red, neutrophils stain a neutral pink. Norm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chloride Peroxidase
Chloride peroxidase () is a family of enzymes that catalyzes the chlorination of organic compounds. This enzyme combines the inorganic substrates chloride and hydrogen peroxide to produce the equivalent of Cl+, which replaces a proton in hydrocarbon substrate: :R-H + Cl− + H2O2 + H+ → R-Cl + 2 H2O In fact the source of "Cl+" is hypochlorous acid (HOCl). Many organochlorine compounds are biosynthesized in this way. This enzyme belongs to the family of oxidoreductases, specifically those acting on a peroxide as acceptors (peroxidases). The systematic name of this enzyme class is chloride:hydrogen-peroxide oxidoreductase. This enzyme is also called chloroperoxidase. It employs one cofactor which may be either heme or vanadium. (this paper also discussed chloroperoxidases. The heme-containing chloroperoxidase (CPO) exhibits peroxidase, catalase and cytochrome P450-like activities in addition to catalyzing halogenation reactions. Despite functional similarities with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tyrian Purple
Tyrian purple ( grc, πορφύρα ''porphúra''; la, purpura), also known as Phoenician red, Phoenician purple, royal purple, imperial purple, or imperial dye, is a reddish-purple natural dye. The name Tyrian refers to Tyre, Lebanon. It is secreted by several species of predatory sea snails in the family Muricidae, rock snails originally known by the name 'Murex'. In ancient times, extracting this dye involved tens of thousands of snails and substantial labor, and as a result, the dye was highly valued. The colored compound is 6,6′-dibromoindigo. History Biological pigments were often difficult to acquire, and the details of their production were kept secret by the manufacturers. Tyrian purple is a pigment made from the mucus of several species of Murex snail. Production of Tyrian purple for use as a fabric dye began as early as 1200 BCE by the Phoenicians, and was continued by the Greeks and Romans until 1453 CE, with the fall of Constantinople. The pigment wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bromoperoxidase
Bromide peroxidase (, ''bromoperoxidase'', ''haloperoxidase (ambiguous)'', ''eosinophil peroxidase'') is a family of enzymes with systematic name ''bromide:hydrogen-peroxide oxidoreductase''. These enzymes catalyses the following chemical reaction: : HBr + H2O2 \rightleftharpoons HOBr + H2O The HOBr is a potent brominating agent. The many organobromine compounds observed in marine environments are the products of reaction with this oxidized form of bromine. Bromo peroxidases of red and brown marine algae (''Rhodophyta'' and ''Phaeophyta'') contain vanadate ( vanadium bromoperoxidase). Otherwise vanadium is unusual cofactor in biology. By virtue of this family of enzymes, a variety of brominated natural products have been isolated from marine sources. Related chloroperoxidase enzymes effect chlorination. In the nomenclature of haloperoxidase, bromoperoxidases classically are unable to oxidize chloride at all. For example, eosinophil peroxidase appears to prefer bromide ov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Murex
''Murex'' is a genus of medium to large sized predatory tropical sea snails. These are carnivorous marine gastropod molluscs in the family Muricidae, commonly called "murexes" or "rock snails".Houart, R.; Gofas, S. (2010). Murex Linnaeus, 1758. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=138196 on 2011-04-09 The common name murex is still used for many species in the family Muricidae which were originally given the Latin generic name ''Murex'' in the past, but have more recently been regrouped into different newer genera. The word ''murex'' was used by Aristotle in reference to these kinds of snails, thus making it one of the oldest classical seashell names still in use by the scientific community. Fossil records This genus is known in the fossil records from the Cretaceous to the Quaternary (age range: from 125.45 to 0.0 million ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vanadate
In chemistry, a vanadate is an anionic coordination complex of vanadium. Often vanadate refers to oxoanions of vanadium, most of which exist in its highest oxidation state of +5. The complexes and are referred to as hexacyanovanadate(III) and nonachlorodivanadate(III), respectively. A simple vanadate ion is the tetrahedral orthovanadate anion, (which is also called vanadate(V)), which is present in e.g. sodium orthovanadate and in solutions of in strong base ( pH > 13). Conventionally this ion is represented with a single double bond, however this is a resonance form as the ion is a regular tetrahedron with four equivalent oxygen atoms. Additionally a range of polyoxovanadate ions exist which include discrete ions and "infinite" polymeric ions. There are also vanadates, such as rhodium vanadate, , which has a statistical rutile structure where the and ions randomly occupy the positions in the rutile lattice, that do not contain a lattice of cations and balancing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horseradish Peroxidase
The enzyme horseradish peroxidase (HRP), found in the roots of horseradish, is used extensively in biochemistry applications. It is a metalloenzyme with many isoforms, of which the most studied type is C. It catalyzes the oxidation of various organic substrates by hydrogen peroxide. Structure The structure of the enzyme was first solved by X-ray crystallography in 1997; and has since been solved several times with various substrates. It is a large alpha-helical glycoprotein which binds heme as a redox cofactor. Substrates Alone, the HRP enzyme, or conjugates thereof, is of little value; its presence must be made visible using a substrate that, when oxidized by HRP using hydrogen peroxide as the oxidizing agent, yields a characteristic color change that is detectable by spectrophotometric methods. Numerous substrates for horseradish peroxidase have been described and commercialized to exploit the desirable features of HRP. These substrates fall into several distinct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methionine
Methionine (symbol Met or M) () is an essential amino acid in humans. As the precursor of other amino acids such as cysteine and taurine, versatile compounds such as SAM-e, and the important antioxidant glutathione, methionine plays a critical role in the metabolism and health of many species, including humans. It is encoded by the codon AUG. Methionine is also an important part of angiogenesis, the growth of new blood vessels. Supplementation may benefit those suffering from copper poisoning. Overconsumption of methionine, the methyl group donor in DNA methylation, is related to cancer growth in a number of studies. Methionine was first isolated in 1921 by John Howard Mueller. Biochemical details Methionine (abbreviated as Met or M; encoded by the codon AUG) is an α-amino acid that is used in the biosynthesis of proteins. It contains a carboxyl group (which is in the deprotonated −COO− form under biological pH conditions), an amino group (which is in the protonat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
