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Decarboxylase
Carboxy-lyases, also known as decarboxylases, are carbon–carbon lyases that add or remove a carboxyl group from organic compounds. These enzymes catalyze the decarboxylation of amino acids, beta-keto acids and alpha-keto acids. Classification and nomenclature Carboxy-lyases are categorized under EC number 4.1.1. Usually, they are named after the substrate whose decarboxylation they catalyze, for example pyruvate decarboxylase catalyzes the decarboxylation of pyruvate. Examples * Aromatic-L-amino-acid decarboxylase * Glutamate decarboxylase * Histidine decarboxylase * Ornithine decarboxylase * Phosphoenolpyruvate carboxylase * Pyruvate decarboxylase * RuBisCO – the only carboxylase that leads to a net fixation of carbon dioxide * Uridine monophosphate synthetase * Uroporphyrinogen III decarboxylase * enoyl-CoA carboxylases/reductases (ECRs) See also * Enzymes * Lyase In biochemistry, a lyase is an enzyme that catalyzes the breaking (an elimination reaction) of various che ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Histidine Decarboxylase
The enzyme histidine decarboxylase (, HDC) is transcribed on chromosome 15, region 21.2, and catalyzes the decarboxylation of histidine to form histamine. In mammals, histamine is an important biogenic amine with regulatory roles in neurotransmission, gastric acid secretion and immune response. Histidine decarboxylase is the sole member of the histamine synthesis pathway, producing histamine in a one-step reaction. Histamine cannot be generated by any other known enzyme. HDC is therefore the primary source of histamine in most mammals and eukaryotes. The enzyme employs a pyridoxal 5'-phosphate (PLP) cofactor, in similarity to many amino acid decarboxylases. Eukaryotes, as well as gram-negative bacteria share a common HDC, while gram-positive bacteria employ an evolutionarily unrelated pyruvoyl-dependent HDC. In humans, histidine decarboxylase is encoded by the ''HDC'' gene. Structure Histidine decarboxylase is a group II pyridoxal-dependent decarboxylase, along with aromati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyruvate Decarboxylase
Pyruvate decarboxylase is an enzyme () that catalyses the decarboxylation of pyruvic acid to acetaldehyde. It is also called 2-oxo-acid carboxylase, alpha-ketoacid carboxylase, and pyruvic decarboxylase. In anaerobic conditions, this enzyme is participates in the fermentation process that occurs in yeast, especially of the genus ''Saccharomyces'', to produce ethanol by fermentation. It is also present in some species of fish (including goldfish and carp) where it permits the fish to perform ethanol fermentation (along with lactic acid fermentation) when oxygen is scarce. Pyruvate decarboxylase starts this process by converting pyruvate into acetaldehyde and carbon dioxide. Pyruvate decarboxylase depends on cofactors thiamine pyrophosphate (TPP) and magnesium. This enzyme should not be mistaken for the unrelated enzyme pyruvate dehydrogenase, an oxidoreductase (), that catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA. Structure Pyruvate decarboxylase occurs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glutamate Decarboxylase
Glutamate decarboxylase or glutamic acid decarboxylase (GAD) is an enzyme that catalyzes the decarboxylation of glutamate to gamma-aminobutyric acid (GABA) and carbon dioxide (). GAD uses pyridoxal-phosphate (PLP) as a cofactor. The reaction proceeds as follows: : In mammals, GAD exists in two isoforms with molecular weights of 67 and 65 kDa (GAD67 and GAD65), which are encoded by two different genes on different chromosomes (GAD1 and GAD2 genes, chromosomes 2 and 10 in humans, respectively). GAD67 and GAD65 are expressed in the brain where GABA is used as a neurotransmitter, and they are also expressed in the insulin-producing β-cells of the pancreas, in varying ratios depending upon the species. Together, these two enzymes maintain the major physiological supply of GABA in mammals, though it may also be synthesized from putrescine in the enteric nervous system, brain, and elsewhere by the actions of diamine oxidase and aldehyde dehydrogenase 1a1. Several truncated tra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ornithine Decarboxylase
The enzyme ornithine decarboxylase (, ODC) catalyzes the decarboxylation of ornithine (a product of the urea cycle) to form putrescine. This reaction is the committed step in polyamine synthesis. In humans, this protein has 461 amino acids and forms a homodimer. Reaction mechanism Lysine 69 on ornithine decarboxylase (ODC) binds the cofactor pyridoxal phosphate to form a Schiff base. Ornithine displaces the lysine to form a Schiff base attached to orthonine, which decarboxylates to form a quinoid intermediate. This intermediate rearranges to form a Schiff base attached to putrescine, which is attacked by lysine to release putrescine product and reform PLP-bound ODC. This is the first step and the rate-limiting step in humans for the production of polyamines, compounds required for cell division. Structure image:Ornithine Decarboxylase Publication View.png, 270px, 3D crystal structure of ornithine decarboxylase.; ; rendered viPyMOL The active form of ornithine decarboxylas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme Commission Number
The Enzyme Commission number (EC number) is a numerical classification scheme for enzymes, based on the chemical reactions they catalyze. As a system of enzyme nomenclature, every EC number is associated with a recommended name for the corresponding enzyme-catalyzed reaction. EC numbers do not specify enzymes but enzyme-catalyzed reactions. If different enzymes (for instance from different organisms) catalyze the same reaction, then they receive the same EC number. Furthermore, through convergent evolution, completely different protein folds can catalyze an identical reaction (these are sometimes called non-homologous isofunctional enzymes) and therefore would be assigned the same EC number. By contrast, UniProt identifiers uniquely specify a protein by its amino acid sequence. Format of number Every enzyme code consists of the letters "EC" followed by four numbers separated by periods. Those numbers represent a progressively finer classification of the enzyme. Preliminary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aromatic-L-amino-acid Decarboxylase
Aromatic L-amino acid decarboxylase (AADC or AAAD), also known as DOPA decarboxylase (DDC), tryptophan decarboxylase, and 5-hydroxytryptophan decarboxylase, is a lyase enzyme (), located in region 7p12.2-p12.1. Mechanism The enzyme uses pyridoxal phosphate (PLP), the active form of vitamin B6, as a cofactor. PLP is essential to the mechanism of decarboxylation in AADC. In the active enzyme, PLP is bound to lysine-303 of AADC as a Schiff base. Upon substrate binding, Lys-303 is displaced by the substrate's amine. This positions the carboxylate of the substrate within the active site such that decarboxylation is favored. Decarboxylation of the substrate produces a quinonoid intermediate, which is subsequently protonated to produce a Schiff base adduct of PLP and the decarboxylated product. Lys-303 can then regenerate the original Schiff base, releasing the product while retaining PLP. Probing this PLP-catalyzed decarboxylation, it has been discovered that there is a difference ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lyase
In biochemistry, a lyase is an enzyme that catalyzes the breaking (an elimination reaction) of various chemical bond A chemical bond is a lasting attraction between atoms or ions that enables the formation of molecules and crystals. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds, or through the sharing o ...s by means other than hydrolysis (a substitution reaction) and oxidation, often forming a new double bond or a new ring structure. The reverse reaction is also possible (called a Michael reaction). For example, an enzyme that catalyzed this reaction would be a lyase: :Adenosine triphosphate, ATP → cyclic adenosine monophosphate, cAMP + PPi Lyases differ from other enzymes in that they require only one substrate (chemistry), substrate for the reaction in one direction, but two substrates for the reverse reaction. Nomenclature Systematic names are formed as "''substrate group-lyase''." Common names include decarboxyl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme
Enzymes () are proteins that act as biological catalysts 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 are Ribozyme, catalytic RNA molecules, called ribozymes. Enzymes' Chemical specificity, specific ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uroporphyrinogen III Decarboxylase
Uroporphyrinogen III decarboxylase (uroporphyrinogen decarboxylase, or UROD) is an enzyme () that in humans is encoded by the ''UROD'' gene. Function Uroporphyrinogen III decarboxylase is a homodimeric enzyme () that catalyzes the fifth step in heme biosynthesis, which corresponds to the elimination of carboxyl groups from the four acetate side chains of uroporphyrinogen III to yield coproporphyrinogen III: :uroporphyrinogen III \rightleftharpoons coproporphyrinogen III + 4 CO2 Clinical significance Mutations and deficiency in this enzyme are known to cause familial porphyria cutanea tarda and hepatoerythropoietic porphyria. At least 65 disease-causing mutations in this gene have been discovered. Mechanism At low substrate concentrations, the reaction is believed to follow an ordered route, with the sequential removal of CO2 from the D, A, B, and C rings, whereas at higher substrate/enzyme levels a random route seems to be operative. The enzyme functions as a dimer in s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uridine Monophosphate Synthetase
The enzyme Uridine monophosphate synthase (, UMPS) (orotate phosphoribosyl transferase and orotidine-5'-decarboxylase) catalyses the formation of uridine monophosphate (UMP), an energy-carrying molecule in many important biosynthetic pathways. In humans, the gene that codes for this enzyme is located on the long arm of chromosome 3 (3q13). Structure and function This bifunctional enzyme has two main domains, an orotate phosphoribosyltransferase (OPRTase, ) subunit and an orotidine-5’-phosphate decarboxylase (ODCase, ) subunit. These two sites catalyze the last two steps of the de novo uridine monophosphate (UMP) biosynthetic pathway. After addition of ribose-P to orotate by OPRTase to form orotidine-5’-monophosphate (OMP), OMP is decarboxylated to form uridine monophosphate by ODCase. In microorganisms, these two domains are separate proteins, but, in multicellular eukaryotes, the two catalytic sites are expressed on a single protein, uridine monophosphate synthase. UMPS ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RuBisCO
Ribulose-1,5-bisphosphate carboxylase-oxygenase, commonly known by the abbreviations RuBisCo, rubisco, RuBPCase, or RuBPco, is an enzyme () involved in the first major step of carbon fixation, a process by which atmospheric carbon dioxide is converted by plants and other photosynthetic organisms to energy-rich molecules such as glucose. In chemical terms, it catalyzes the carboxylation of ribulose-1,5-bisphosphate (also known as RuBP). It is probably the most abundant enzyme on Earth. Alternative carbon fixation pathways RuBisCO is important biologically because it catalyzes the primary chemical reaction by which inorganic carbon enters the biosphere. While many autotrophic bacteria and archaea fix carbon via the reductive acetyl CoA pathway, the 3-hydroxypropionate cycle, or the reverse Krebs cycle, these pathways are relatively small contributors to global carbon fixation compared to that catalyzed by RuBisCO. Phosphoenolpyruvate carboxylase, unlike RuBisCO, only te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
