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Carbamoyl Phosphate Synthetase
Carbamoyl phosphate synthetase catalyzes the ATP-dependent synthesis of carbamoyl phosphate from glutamine () or ammonia () and bicarbonate. This enzyme catalyzes the reaction of ATP and bicarbonate to produce carboxy phosphate and ADP. Carboxy phosphate reacts with ammonia to give carbamic acid. In turn, carbamic acid reacts with a second ATP to give carbamoyl phosphate plus ADP. It represents the first committed step in pyrimidine and arginine biosynthesis in prokaryotes and eukaryotes, and in the urea cycle in most terrestrial vertebrates. Most prokaryotes carry one form of CPSase that participates in both arginine and pyrimidine biosynthesis, however certain bacteria can have separate forms. There are three different forms that serve very different functions: * Carbamoyl phosphate synthetase I (mitochondria, urea cycle) * Carbamoyl phosphate synthetase II (cytosol, pyrimidine metabolism). * Carbamoyl phosphate synthetase III (found in fish). Mechanism Carbamoyl phos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbamoyl Phosphate Synthetase II
Carbamoyl phosphate synthetase (glutamine-hydrolysing) () is an enzyme that catalyzes the reactions that produce carbamoyl phosphate in the cytosol (as opposed to type I, which functions in the mitochondria). Its systemic name is ''hydrogen-carbonate:L-glutamine amido-ligase (ADP-forming, carbamate-phosphorylating)''. In pyrimidine biosynthesis, it serves as the rate-limiting enzyme and catalyzes the following reaction: : 2 ATP + L-glutamine + HCO3− + H2O \rightleftharpoons 2 ADP + phosphate + L-glutamate + carbamoyl phosphate (overall reaction) : (1a) L-glutamine + H2O \rightleftharpoons L-glutamate + NH3 : (1b) 2 ATP + HCO3− + NH3 \rightleftharpoons 2 ADP + phosphate + carbamoyl phosphate It is activated by ATP and PRPP and it is inhibited by UMP (Uridine monophosphate, the end product of the pyrimidine synthesis pathway). Neither CPSI nor CPSII require biotin as a coenzyme, as seen with most carboxylation reactions. It is one of the three enzyme functions coded by the CA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Site
In biology and biochemistry, the active site is the region of an enzyme where substrate molecules bind and undergo a chemical reaction. The active site consists of amino acid residues that form temporary bonds with the substrate (binding site) and residues that catalyse a reaction of that substrate (catalytic site). Although the active site occupies only ~10–20% of the volume of an enzyme, it is the most important part as it directly catalyzes the chemical reaction. It usually consists of three to four amino acids, while other amino acids within the protein are required to maintain the tertiary structure of the enzymes. Each active site is evolved to be optimised to bind a particular substrate and catalyse a particular reaction, resulting in high specificity. This specificity is determined by the arrangement of amino acids within the active site and the structure of the substrates. Sometimes enzymes also need to bind with some cofactors to fulfil their function. The active si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Domain
In molecular biology, a protein domain is a region of a protein's polypeptide chain that is self-stabilizing and that folds independently from the rest. Each domain forms a compact folded three-dimensional structure. Many proteins consist of several domains, and a domain may appear in a variety of different proteins. Molecular evolution uses domains as building blocks and these may be recombined in different arrangements to create proteins with different functions. In general, domains vary in length from between about 50 amino acids up to 250 amino acids in length. The shortest domains, such as zinc fingers, are stabilized by metal ions or disulfide bridges. Domains often form functional units, such as the calcium-binding EF hand domain of calmodulin. Because they are independently stable, domains can be "swapped" by genetic engineering between one protein and another to make chimeric proteins. Background The concept of the domain was first proposed in 1973 by Wetlaufer aft ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synthetase
In biochemistry, a ligase is an enzyme that can catalyze the joining (Ligation (molecular biology), ligation) of two large molecules by forming a new chemical bond. This is typically via hydrolysis of a small pendant chemical group on one of the larger molecules or the enzyme catalyzing the linking together of two compounds, e.g., enzymes that catalyze joining of C-O, C-S, C-N, etc. In general, a ligase catalyzes the following reaction: :Ab + C → A–C + b or sometimes :Ab + cD → A–D + b + c + d + e + f where the lowercase letters can signify the small, dependent groups. Ligase can join two complementary fragments of nucleic acid and repair single stranded breaks that arise in double stranded DNA during replication. Nomenclature The common names of ligases often include the word "ligase", such as DNA ligase, an enzyme commonly used in molecular biology laboratory, laboratories to join together DNA fragments. Other common names for ligases include the word "synth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Fusion
A fusion gene is a hybrid gene formed from two previously independent genes. It can occur as a result of translocation, interstitial deletion, or chromosomal inversion. Fusion genes have been found to be prevalent in all main types of human neoplasia. The identification of these fusion genes play a prominent role in being a diagnostic and prognostic marker. History The first fusion gene was described in cancer cells in the early 1980s. The finding was based on the discovery in 1960 by Peter Nowell and David Hungerford in Philadelphia of a small abnormal marker chromosome in patients with chronic myeloid leukemia—the first consistent chromosome abnormality detected in a human malignancy, later designated the Philadelphia chromosome. In 1973, Janet Rowley in Chicago showed that the Philadelphia chromosome had originated through a translocation between chromosomes 9 and 22, and not through a simple deletion of chromosome 22 as was previously thought. Several investigators in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polypeptide
Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A polypeptide is a longer, continuous, unbranched peptide chain. Hence, peptides fall under the broad chemical classes of biological polymers and oligomers, alongside nucleic acids, oligosaccharides, polysaccharides, and others. A polypeptide that contains more than approximately 50 amino acids is known as a protein. Proteins consist of one or more polypeptides arranged in a biologically functional way, often bound to ligands such as coenzymes and cofactors, or to another protein or other macromolecule such as DNA or RNA, or to complex macromolecular assemblies. Amino acids that have been incorporated into peptides are termed residues. A water molecule is released during formation of each amide bond.. All peptides except cyclic peptides ... [...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 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] |
Protein Dimer
In biochemistry, a protein dimer is a macromolecular complex formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ''dimer'' has roots meaning "two parts", '' di-'' + '' -mer''. A protein dimer is a type of protein quaternary structure. A protein homodimer is formed by two identical proteins. A protein heterodimer is formed by two different proteins. Most protein dimers in biochemistry are not connected by covalent bonds. An example of a non-covalent heterodimer is the enzyme reverse transcriptase, which is composed of two different amino acid chains. An exception is dimers that are linked by disulfide bridges such as the homodimeric protein NEMO. Some proteins contain specialized domains to ensure dimerization (dimerization domains) and specificity. The G protein-coupled cannabinoid receptors have the ability to form both homo- and heterodimers with several ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synthase
In biochemistry, a synthase is an enzyme that catalyses a synthesis process. Note that, originally, biochemical nomenclature distinguished synthetases and synthases. Under the original definition, synthases do not use energy from nucleoside triphosphates (such as ATP, GTP, CTP, TTP, and UTP), whereas synthetases do use nucleoside triphosphates. However, the Joint Commission on Biochemical Nomenclature (JCBN) dictates that 'synthase' can be used with any enzyme that catalyzes synthesis (whether or not it uses nucleoside triphosphates), whereas 'synthetase' is to be used synonymously with 'ligase'. Examples * ATP synthase * Citrate synthase * Tryptophan synthase * Pseudouridine synthase * Fatty acid synthase * Cellulose synthase (UDP-forming) * Cellulose synthase (GDP-forming) In enzymology, a cellulose synthase (GDP-forming) () is an enzyme that catalyzes the chemical reaction :GDP-glucose + (1,4-beta-D-glucosyl)n \rightleftharpoons GDP + (1,4-beta-D-glucosyl)n+1 Thus, the tw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphate
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosphoric acid by the removal of three protons . Removal of one or two protons gives the dihydrogen phosphate ion and the hydrogen phosphate ion ion, respectively. These names are also used for salts of those anions, such as ammonium dihydrogen phosphate and trisodium phosphate. File:3-phosphoric-acid-3D-balls.png, Phosphoricacid File:2-dihydrogenphosphate-3D-balls.png, Dihydrogenphosphate File:1-hydrogenphosphate-3D-balls.png, Hydrogenphosphate File:0-phosphate-3D-balls.png, Phosphate In organic chemistry, phosphate or orthophosphate is an organophosphate, an ester of orthophosphoric acid of the form where one or more hydrogen atoms are replaced by organic groups. An example is trimethyl phosphate, . The term also refers to the triv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HEPES
HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) is a zwitterionic sulfonic acid buffering agent; one of the twenty Good's buffers. HEPES is widely used in cell culture, largely because it is better at maintaining physiological pH despite changes in carbon dioxide concentration (produced by aerobic respiration) when compared to bicarbonate buffers, which are also commonly used in cell culture. Lepe-Zuniga ''et al.'' reported an unwanted photochemical process wherein HEPES when exposed to ambient light produces hydrogen peroxide, which is not a problem in bicarbonate-based cell culture buffers. It is therefore strongly advised to keep HEPES-containing solutions in darkness as much as possible to prevent oxidation. HEPES has the following characteristics: * p''K''a1 (25 °C) = 3 * p''K''a2 (25 °C) = 7.5 * Useful pH range = 2.5 to 3.5 or 6.8 to 8.2 HEPES has negligible metal ion binding, making it a good choice as a buffer for enzymes which might be inhibited ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
