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P450
Cytochromes P450 (P450s or CYPs) are a superfamily of enzymes containing heme as a cofactor that mostly, but not exclusively, function as monooxygenases. However, they are not omnipresent; for example, they have not been found in ''Escherichia coli''. In mammals, these enzymes oxidize steroids, fatty acids, xenobiotics, and participate in many biosyntheses. By hydroxylation, CYP450 enzymes convert xenobiotics into hydrophilic derivatives, which are more readily excreted. P450s are, in general, the terminal oxidase enzymes in electron transfer chains, broadly categorized as P450-containing systems. The term "P450" is derived from the spectrophotometric peak at the wavelength of the absorption maximum of the enzyme (450 nm) when it is in the reduced state and complexed with carbon monoxide. Most P450s require a protein partner to deliver one or more electrons to reduce the iron (and eventually molecular oxygen). Nomenclature Genes encoding P450 enzymes, and the enzym ... [...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 Mitoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CYP2E1
Cytochrome P450 2E1 (abbreviated CYP2E1, ) is a member of the cytochrome P450 mixed-function oxidase system, which is involved in the metabolism of xenobiotics in the body. This class of enzymes is divided up into a number of subcategories, including CYP1, CYP2, and CYP3, which as a group are largely responsible for the breakdown of foreign compounds in mammals. While CYP2E1 itself carries out a relatively low number of these reactions (~4% of known P450-mediated drug oxidations), it and related enzymes CYP1A2 and CYP3A4 are responsible for the breakdown of many toxic environmental chemicals and carcinogens that enter the body, in addition to basic metabolic reactions such as fatty acid oxidations. CYP2E1 protein localizes to the endoplasmic reticulum and is induced by ethanol, the diabetic state, and starvation. The enzyme metabolizes both endogenous substrates, such as ethanol, acetone, and acetal, as well as exogenous substrates including benzene, carbon tetrachloride, ethyle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CYP51A1
Lanosterol 14α-demethylase (CYP51A1) is the animal version of a cytochrome P450 enzyme that is involved in the conversion of lanosterol to 4,4-dimethylcholesta-8(9),14,24-trien-3β-ol. The cytochrome P450 isoenzymes are a conserved group of proteins that serve as key players in the metabolism of organic substances and the biosynthesis of important steroids, lipids, and vitamins in eukaryotes. As a member of this family, lanosterol 14α-demethylase is responsible for an essential step in the biosynthesis of sterols. In particular, this protein catalyzes the removal of the C-14α-methyl group from lanosterol. This demethylation step is regarded as the initial checkpoint in the transformation of lanosterol to other sterols that are widely used within the cell. Evolution The structural and functional properties of the cytochrome P450 superfamily have been subject to extensive diversification over the course of evolution. Recent estimates indicate that there are currently 10 clas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thromboxane-A Synthase
Thromboxane A synthase 1 (, platelet, cytochrome P450, family 5, subfamily A), also known as TBXAS1, is a cytochrome P450 enzyme that, in humans, is encoded by the ''TBXAS1'' gene. Function This gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases that catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids, and other lipids. However, this protein is considered a member of the cytochrome P450 superfamily on the basis of sequence similarity rather than functional similarity. This endoplasmic reticulum membrane protein catalyzes the conversion of prostaglandin H2 to thromboxane A2, a potent vasoconstrictor and inducer of platelet aggregation, and also to 12-Hydroxyheptadecatrienoic acid (i.e. 12-(''S'')-hydroxy-5''Z'',8''E'',10''E''-heptadecatrienoic acid or 12-HHT) an agonist of Leukotriene B4 receptors (i.e. BLT2 receptors) and mediator of certain BLT2 receptor actions. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CYP51
In enzymology, a sterol 14-demethylase () is an enzyme of the cytochrome P450 (CYP) superfamily. It is any member of the CYP51 family. It catalysis, catalyzes a chemical reaction such as: :obtusifoliol + 3 O2 + 3 NADPH + 3 H+ \rightleftharpoons 4alpha-methyl-5alpha-ergosta-8,14,24(28)-trien-3beta-ol + formate + 3 NADP+ + 4 H2O The 4 substrate (biochemistry), substrates here are obtusifoliol, oxygen, O2, nicotinamide adenine dinucleotide phosphate, NADPH, and hydrogen ion, H+, whereas its 4 product (chemistry), products are 4alpha-methyl-5alpha-ergosta-8,14,24(28)-trien-3beta-ol, formate, nicotinamide adenine dinucleotide phosphate, NADP+, and water, H2O. Although the lanosterol 14α-demethylase is present in a wide variety of organisms, the enzyme is studied primarily in the context of fungi, where it plays an essential role in mediating membrane permeability. In fungi, CYP51 catalyzes the demethylation of lanosterol to create an important precursor that is eventually converted ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steroid
A steroid is an organic compound with four fused compound, fused rings (designated A, B, C, and D) arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and as signal transduction, signaling molecules. Examples include the lipid cholesterol, sex hormones estradiol and testosterone, anabolic steroids, and the anti-inflammatory corticosteroid drug dexamethasone. Hundreds of steroids are found in Fungus, fungi, plants, and animals. All steroids are manufactured in cells from a sterols, sterol: Cholesterol, cholesterol (animals), lanosterol (opisthokonts), or cycloartenol (plants). All three of these molecules are produced via Cyclic compound, cyclization of the triterpene squalene. Structure The steroid nucleus (parent structure, core structure) is called gonane (cyclopentanoperhydrophenanthrene). It is typically composed of seventeen carbon atoms, bonded in fou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paracetamol
Paracetamol, or acetaminophen, is a non-opioid analgesic and antipyretic agent used to treat fever and mild to moderate pain. It is a widely available over-the-counter drug sold under various brand names, including Tylenol and Panadol. Paracetamol relieves pain in both acute mild migraine and episodic tension headache. At a standard dose, paracetamol slightly reduces fever, though it is inferior to ibuprofen in that respect and the benefits of its use for fever are unclear, particularly in the context of fever of viral origins. The aspirin/paracetamol/caffeine combination also helps with both conditions when the pain is mild and is recommended as a Therapy#Lines of therapy, first-line treatment for them. Paracetamol is effective for post-surgical pain, but is inferior to ibuprofen for this purpose. The paracetamol/ibuprofen combination increases the drugs' potency and is superior to either drug alone. The pain relief paracetamol provides in osteoarthritis is small and clinica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xenobiotic
A xenobiotic is a chemical substance found within an organism that is not naturally produced or expected to be present within the organism. It can also cover substances that are present in much higher concentrations than are usual. Natural compounds can also become xenobiotics if they are taken up by another organism, such as the uptake of natural human hormones by fish found downstream of sewage treatment plant outfalls, or the chemical defenses produced by some organisms as protection against predators. The term "xenobiotic" is also used to refer to organs transplanted from one species to another. The term "xenobiotics", however, is very often used in the context of pollutants such as dioxins and polychlorinated biphenyls and their effect on the biota, because xenobiotics are understood as substances foreign to an entire biological system, i.e. artificial substances, which did not exist in nature before their synthesis by humans. The term xenobiotic is derived from the Gree ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monooxygenase
Monooxygenases are enzymes that incorporate one hydroxyl group (−OH) into substrates in many metabolic pathways. In this reaction, the two atoms of dioxygen are reduced to one hydroxyl group and one H2O molecule by the concomitant oxidation of NAD(P)H. One important subset of the monooxygenases, the cytochrome P450 omega hydroxylases, is used by cells to metabolize arachidonic acid (i.e. eicosatetraenoic acid) to the cell signaling molecules, 20-hydroxyeicosatetraenoic acid or to reduce or totally inactivate the activate signaling molecules for example by hydroxylating leukotriene B4 to 20-hydroxy-leukotriene B5, 5-hydroxyeicosatetraenoic acid to 5,20-dihydroxyeicosatetraenoic acid, 5-oxo-eicosatetraenoic acid to 5-oxo-20-hydroxyeicosatetraenoic acid, 12-hydroxyeicosatetraenoic acid to 12,20-dihydroxyeicosatetraenoic acid, and epoxyeicosatrienoic acids to 20-hydroxy-epoxyeicosatrienoic acids. Classification They are classified as oxidoreductase enzymes that catalyze an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's outer and inner core. It is the fourth most abundant element in the Earth's crust, being mainly deposited by meteorites in its metallic state. Extracting usable metal from iron ores requires kilns or furnaces capable of reaching , about 500 °C (900 °F) higher than that required to smelt copper. Humans started to master that process in Eurasia during the 2nd millennium BC and the use of iron tools and weapons began to displace copper alloys – in some regions, only around 1200 BC. That event is considered the transition from the Bronze Age to the Iron Age. In the modern world, iron alloys, such as steel, stainless steel, cast iron and special steels, are by far the most common industrial metals, due to their mechan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme
An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecules known as product (chemistry), products. Almost all metabolism, metabolic processes in the cell (biology), cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Metabolic pathways depend upon enzymes to catalyze individual steps. The study of enzymes is called ''enzymology'' and the field of pseudoenzyme, pseudoenzyme analysis recognizes that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual 'pseudocatalytic' properties. Enzymes are known to catalyze more than 5,000 biochemical reaction types. Other biocatalysts include Ribozyme, catalytic RNA molecules, also called ribozymes. They are sometimes descr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
