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Cytochrome B5
Cytochromes ''b''5 are ubiquitous electron transport hemoproteins found in animals, plants, fungi and purple phototrophic bacteria. The microsomal and mitochondrial variants are membrane-bound, while bacterial and those from erythrocytes and other animal tissues are water-soluble. The family of cytochrome ''b''5-like proteins includes (besides cytochrome ''b''5 itself) hemoprotein domains covalently associated with other redox domains in flavocytochrome cytochrome ''b''2 (L-lactate dehydrogenase; ), sulfite oxidase (), plant and fungal nitrate reductases (, , ), and plant and fungal cytochrome ''b''5/acyl lipid desaturase fusion proteins. Structure 3-D structures of a number of cytochrome ''b''5 and yeast flavocytochrome ''b''2 are known. The fold belongs to the α+β class, with two hydrophobic cores on each side of a β-sheet. The larger hydrophobic core constitutes the heme-binding pocket, closed off on each side by a pair of helices connected by a turn. The smaller hydro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cofactor (biochemistry)
A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme's role as a catalyst (a catalyst is a substance that increases the rate of a chemical reaction). Cofactors can be considered "helper molecules" that assist in biochemical transformations. The rates at which these happen are characterized in an area of study called enzyme kinetics. Cofactors typically differ from ligands in that they often derive their function by remaining bound. Cofactors can be divided into two types: inorganic ions and complex organic molecules called coenzymes. Coenzymes are mostly derived from vitamins and other organic essential nutrients in small amounts. (Note that some scientists limit the use of the term "cofactor" for inorganic substances; both types are included here.) Coenzymes are further divided into two types. The first is called a "prosthetic group", which consists of a coenzyme that is tightly (or even covalently) and permanently bound to a protein. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erythrocyte
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "hollow vessel", with ''-cyte'' translated as "cell" in modern usage), are the most common type of blood cell and the vertebrate's principal means of delivering oxygen (O2) to the body tissues—via blood flow through the circulatory system. RBCs take up oxygen in the lungs, or in fish the gills, and release it into tissues while squeezing through the body's capillaries. The cytoplasm of a red blood cell is rich in hemoglobin, an iron-containing biomolecule that can bind oxygen and is responsible for the red color of the cells and the blood. Each human red blood cell contains approximately 270 million hemoglobin molecules. The cell membrane is composed of proteins and lipids, and this structure provides properties essential for physiologi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
P450-containing Systems
Any enzyme system that includes cytochrome P450 protein or domain can be called a P450-containing system. P450 enzymes usually function as a terminal oxidase in multicomponent electron-transfer chains, called P450-containing monooxygenase systems, although self-sufficient, non-monooxygenase P450s have been also described. All known P450-containing monooxygenase systems share common structural and functional domain architecture. Apart from the cytochrome itself, these systems contain one or more fundamental redox domains: FAD-containing flavoprotein or domain, FMN domain, ferredoxin and cytochrome ''b''5. These ubiquitous redox domains, in various combinations, are widely distributed in biological systems. FMN domain, ferredoxin or cytochrome ''b''5 transfer electrons between the flavin reductase (protein or domain) and P450. While P450-containing systems are found throughout all kingdoms of life, some organisms lack one or more of these redox domains. FR/Fd/P450 systems Mitocho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytochrome B5 Deficiency
Cytochrome b5 deficiency is a rare condition and form of isolated 17,20-lyase deficiency caused by deficiency in cytochrome b5, a small hemoprotein that acts as an allosteric factor to facilitate the interaction of CYP17A1 (17α-hydroxylase/17,20-lyase) with P450 oxidoreductase (POR), thereby allowing for the 17,20-lyase activity of CYP17A1. The condition affects both adrenal and gonadal androgen biosynthesis and results in male pseudohermaphroditism. The principal biological role of cytochrome b5 is reduction of methemoglobin Methemoglobin (British: methaemoglobin) (pronounced "met-hemoglobin") is a hemoglobin ''in the form of metalloprotein'', in which the iron in the heme group is in the Fe3+ (ferric) state, not the Fe2+ (ferrous) of normal hemoglobin. Sometimes, it i ..., so cytochrome b5 deficiency can also result in elevated methemoglobin levels and/or methemoglobinemia, similarly to deficiency of cytochrome b5 reductase (methemoglobin reductase). References Extern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytochrome B
Cytochrome b within both molecular and cell biology, is a protein found in the mitochondria of eukaryotic cells. It functions as part of the electron transport chain and is the main subunit of transmembrane cytochrome bc1 and b6f complexes. Function In the mitochondrion of eukaryotes and in aerobic prokaryotes, cytochrome b is a component of respiratory chain complex III () — also known as the bc1 complex or ubiquinol-cytochrome c reductase. In plant chloroplasts and cyanobacteria, there is an analogous protein, cytochrome b6, a component of the plastoquinone-plastocyanin reductase (), also known as the b6f complex. These complexes are involved in electron transport, the pumping of protons to create a proton-motive force ( PMF). This proton gradient is used for the generation of ATP. These complexes play a vital role in cells. Structure Cytochrome b/b6 is an integral membrane protein of approximately 400 amino acid residues that probably has 8 transmembrane segments. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stearoyl-CoA 9-desaturase
Stearoyl-CoA desaturase (Δ-9-desaturase) is an endoplasmic reticulum enzyme that catalyzes the rate-limiting step in the formation of monounsaturated fatty acids (MUFAs), specifically oleate and palmitoleate from stearoyl-CoA and palmitoyl-CoA. Oleate and palmitoleate are major components of membrane phospholipids, cholesterol esters and alkyl-diacylglycerol. In humans, the enzyme is encoded by the SCD gene. Stearoyl-CoA desaturase-1 is a key enzyme in fatty acid metabolism. It is responsible for forming a double bond in Stearoyl-CoA. This is how the monounsaturated fatty acid oleic acid is produced from the saturated fatty acid stearic acid. A series of redox reactions, during which two electrons flow from NADH to flavoprotein cytochrome b5, then to the electron acceptor cytochrome b5 as well as molecular oxygen introduces a single double bond within a row of methylene fatty acyl-CoA substrates. The complexed enzyme adds a single double bond between the C9 and C10 of lon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CMP-N-acetylneuraminate Monooxygenase
In enzymology, a CMP-N-acetylneuraminate monooxygenase () is an enzyme that catalyzes the chemical reaction :CMP-N-acetylneuraminate + 2 ferrocytochrome b5 + O2 + 2 H+ \rightleftharpoons CMP-N-glycoloylneuraminate + 2 ferricytochrome b5 + H2O The 4 substrates of this enzyme are CMP-N-acetylneuraminate, ferrocytochrome b5, O2, and H+, whereas its 3 products are CMP-N-glycoloylneuraminate, ferricytochrome b5, and H2O. This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with another compound as one donor, and incorporation of one atom o oxygen into the other donor. The systematic name of this enzyme class is CMP-N-acetylneuraminate,ferrocytochrome-b5:oxygen oxidoreductase (N-acetyl-hydroxylating). Other names in common use include CMP-N-acetylneuraminic acid hydroxylase, CMP-Neu5Ac hydroxylase, cytidine monophosphoac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
L-ascorbate-cytochrome-b5 Reductase
Ascorbate ferrireductase (transmembrane) (, '' cytochrome b561'') is an enzyme with systematic name ''Fe(III):ascorbate oxidorectuctase (electron-translocating)''. This enzyme catalyses the following chemical reaction ascorbate n/sub> + Fe(III) ut/sub> \rightleftharpoons monodehydroascorbate radical n/sub> + Fe(II) ut/sub> + H+ n/sub> Ascorbate ferrireductase is a diheme cytochrome that acts on hexacyanoferrate(III) and other ferric chelates. Ferric Fe(III) and Ferrous Fe(II) Solubility Using the conversion of ascorbate (Vitamin C) to monodehydroascorbate is essential when the ferric Fe(III) ion is converted to ferrous Fe(II).The Fe(III) species is insoluble, hence becoming one of the most problematic metal species to introduce and dissolve into an organisms system. Especially in eukaryotes such as humans, fungi, and bacteria, the upcycle of ascorbate is very important as well as the bioavailability of the ferrous (II) ion. There are three ways to increase the solubility of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytochrome B5 Reductase
Cytochrome-''b''5 reductase is a NADH-dependent enzyme that converts ferricytochrome from a Fe3+ form to a Fe2+ form. It contains flavin adenine dinucleotide, FAD and catalyzes the reaction: In its b5-reducing capacity, this enzyme is involved in desaturation and elongation of fatty acids, cholesterol biosynthesis, and drug metabolism. This enzyme can also reduce methemoglobin to normal hemoglobin, gaining it the inaccurate synonym methemoglobin reductase. Isoforms expressed in erythrocytes (CYB5R1, CYB5R3) perform this function ''in vivo''. Ferricyanide is another substrate ''in vitro''. The following four human genes encode cytochrome-''b''5 reductases: * CYB5R1 * CYB5R2 * CYB5R3 * CYB5R4 * CYB5RL See also * Cytochrome b5 * Diaphorase * Methemoglobinemia * Reductase * Leghemoglobin reductase References External links * {{Portal bar, Biology, border=no EC 1.6.2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biological Tissue
In biology, tissue is a biological organizational level between cells and a complete organ. A tissue is an ensemble of similar cells and their extracellular matrix from the same origin that together carry out a specific function. Organs are then formed by the functional grouping together of multiple tissues. The English word "tissue" derives from the French word "tissu", the past participle of the verb tisser, "to weave". The study of tissues is known as histology or, in connection with disease, as histopathology. Xavier Bichat is considered as the "Father of Histology". Plant histology is studied in both plant anatomy and physiology. The classical tools for studying tissues are the paraffin block in which tissue is embedded and then sectioned, the histological stain, and the optical microscope. Developments in electron microscopy, immunofluorescence, and the use of frozen tissue-sections have enhanced the detail that can be observed in tissues. With these tools, the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitochondria
A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used throughout the cell as a source of chemical energy. They were discovered by Albert von Kölliker in 1857 in the voluntary muscles of insects. The term ''mitochondrion'' was coined by Carl Benda in 1898. The mitochondrion is popularly nicknamed the "powerhouse of the cell", a phrase coined by Philip Siekevitz in a 1957 article of the same name. Some cells in some multicellular organisms lack mitochondria (for example, mature mammalian red blood cells). A large number of unicellular organisms, such as microsporidia, parabasalids and diplomonads, have reduced or transformed their mitochondria into mitosome, other structures. One eukaryote, ''Monocercomonoides'', is known to have completely lost its mitocho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haem
Heme, or haem (pronounced / hi:m/ ), is a precursor to hemoglobin, which is necessary to bind oxygen in the bloodstream. Heme is biosynthesized in both the bone marrow and the liver. In biochemical terms, heme is a coordination complex "consisting of an iron ion coordinated to a porphyrin acting as a tetradentate ligand, and to one or two axial ligands." The definition is loose, and many depictions omit the axial ligands. Among the metalloporphyrins deployed by metalloproteins as prosthetic groups, heme is one of the most widely used and defines a family of proteins known as hemoproteins. Hemes are most commonly recognized as components of hemoglobin, the red pigment in blood, but are also found in a number of other biologically important hemoproteins such as myoglobin, cytochromes, catalases, heme peroxidase, and endothelial nitric oxide synthase. The word ''haem'' is derived from Greek ''haima'' meaning "blood". Function Hemoproteins have diverse biological functions i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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