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Δ7-sterol 5(6)-desaturase
In enzymology, a Δ7-sterol 5(6)-desaturase () is an enzyme that catalyzes the chemical reaction Δ7-sterol + 2 ferrocytochrome b5 + + 2 H+ = Δ5,7-sterol + 2 ferricytochrome b5 + 2 The four substrates of this enzyme are Δ7-sterol, ferrocytochrome b5, H+, and O2. Its three products are Δ5,7-sterol, ferricytochrome b5, and H2O. Classification This enzyme is one of C-5 sterol desaturases, 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 oxidation of a pair of donors resulting in the reduction of molecular oxygen to two molecules of water. Nomenclature The systematic name of this enzyme class is Δ7-sterol,ferrocytochrome b5:oxygen oxidoreductase 5,6-dehydrogenating. Other names in common use include: * lathosterol oxidase * Δ7-sterol Δ5-dehydrogenase * Δ7-sterol 5-desaturase * Δ7-sterol-C5(6)-desatur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzymology
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. Almost all metabolic processes in the 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 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 are catalytic RNA molecules, called ribozymes. Enzymes' specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the reaction ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biosynthesis Of Steroids
A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and as signaling molecules. Hundreds of steroids are found in plants, animals and fungi. All steroids are manufactured in cells from the sterols lanosterol (opisthokonts) or cycloartenol (plants). Lanosterol and cycloartenol are derived from the Cyclic compound, cyclization of the triterpene squalene. The steroid parent structure, core structure is typically composed of seventeen carbon atoms, bonded in four "fused compound, fused" rings: three six-member cyclohexane rings (rings A, B and C in the first illustration) and one five-member cyclopentane ring (the D ring). Steroids vary by the functional groups attached to this four-ring core and by the oxidation state of the rings. Sterols are forms of steroids with a hydroxy group at posit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fatty Acid Desaturase
A fatty acid desaturase is an enzyme that removes two hydrogen atoms from a fatty acid, creating a carbon/carbon double bond. These desaturases are classified as: * Delta - indicating that the double bond is created at a fixed position from the carboxyl end of a fatty acid chain. For example, Δ9 desaturase creates a double bond between the ninth and tenth carbon atom from the carboxyl end. * Omega - indicating the double bond is created at a fixed position from the methyl end of a fatty acid chain. For instance, ω3 desaturase creates a double bond between the third and fourth carbon atom from the methyl end. In other words, it creates an omega-3 fatty acid. For example, Δ6 desaturation introduces a double bond between carbons 6 and 7 of Linoleic acid (LA C18H32O2; 18:2-n6) and α-Linolenic acid (ALA: C18H30O2; 18:3-n3), creating ''γ''-linolenic acid (GLA: C18H30O2,18:3-n6) and stearidonic acid (SDA: C18H28O2; 18:4-n3) respectively. In humans, Δ17-desaturase is able to tur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flavin Mononucleotide
Flavin mononucleotide (FMN), or riboflavin-5′-phosphate, is a biomolecule produced from riboflavin (vitamin B2) by the enzyme riboflavin kinase and functions as the prosthetic group of various oxidoreductases, including NADH dehydrogenase, as well as cofactor in biological blue-light photo receptors. During the catalytic cycle, a reversible interconversion of the oxidized (FMN), semiquinone (FMNH•), and reduced (FMNH2) forms occurs in the various oxidoreductases. FMN is a stronger oxidizing agent than NAD and is particularly useful because it can take part in both one- and two-electron transfers. In its role as blue-light photo receptor, (oxidized) FMN stands out from the 'conventional' photo receptors as the signaling state and not an E/Z isomerization. It is the principal form in which riboflavin is found in cells and tissues. It requires more energy to produce, but is more soluble than riboflavin. In cells, FMN occurs freely circulating but also in several covalently b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flavin Adenine Dinucleotide
Flavin may refer to: Placename * Flavin, Aveyron, a commune in southern France Surname * Adrian Flavin (born 1979), a professional rugby player * Christopher Flavin, president of the Worldwatch Institute * Dan Flavin (1933–1996), a minimalist artist famous for using fluorescent light fixtures * Dan Flavin (politician), Louisiana politician * James Flavin (1906–1976), an American character actor * Jennifer Flavin (born 1968), a former model and wife of actor Sylvester Stallone * Martin Flavin (1883–1967), an American playwright and novelist * Martin Flavin (politician) (1841–1917), Irish Nationalist politician, Member of Parliament (MP) for Cork, 1891–1892 * Michael Joseph Flavin (1866-1944), Irish Nationalist politician, Member of Parliament (MP) for North Kerry, 1896-1918 * Mick Flavin, an Irish country singer Biochemistry * Flavin adenine dinucleotide (FAD), a redox cofactor * Flavin-containing amine oxidoreductase, a family of amine oxidases * Flavin-containing ... [...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] |
Nicotinamide Adenine Dinucleotide Phosphate
Nicotinamide adenine dinucleotide phosphate, abbreviated NADP or, in older notation, TPN (triphosphopyridine nucleotide), is a Cofactor (biochemistry), cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require NADPH as a reducing agent ('hydrogen source'). It is used by all forms of cellular life. NADPH is the redox, reduced form of NADP. NADP differs from NAD+, NAD by the presence of an additional phosphate group on the 2' position of the ribose ring that carries the adenine Moiety (chemistry), moiety. This extra phosphate is added by NAD+ kinase, NAD+ kinase and removed by NADP+ phosphatase. Biosynthesis NADP In general, NADP+ is synthesized before NADPH is. Such a reaction usually starts with NAD+, NAD+ from either the de-novo or the salvage pathway, with NAD+ kinase, NAD+ kinase adding the extra phosphate group. ADP-ribosyl cyclase allows for synthesis from nicotinamide in the salvage pathway, and NADP+ phosphatase ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nicotinamide Adenine Dinucleotide
Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine nucleobase and the other nicotinamide. NAD exists in two forms: an oxidized and reduced form, abbreviated as NAD and NADH (H for hydrogen), respectively. In metabolism, nicotinamide adenine dinucleotide is involved in redox reactions, carrying electrons from one reaction to another. The cofactor is, therefore, found in two forms in cells: NAD is an oxidizing agent – it accepts electrons from other molecules and becomes reduced. This reaction, also with H+, forms NADH, which can then be used as a reducing agent to donate electrons. These electron transfer reactions are the main function of NAD. However, it is also used in other cellular processes, most notably as a substrate of enzymes in adding or removing chemical groups to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
