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Metabolite Damage And Its Repair Or Pre-emption
Metabolite damage can occur through enzyme promiscuity or spontaneous chemical reactions. Many metabolites are Chemical reaction, chemically reactive and unstable and can react with other cell components or undergo unwanted modifications. Enzymatically or chemically damaged metabolites are always useless and often toxic. To prevent toxicity that can occur from the accumulation of damaged metabolites, organisms have damage-control systems that: # Reconvert damaged metabolites to their original, undamaged form (damage repair) # Convert a potentially harmful metabolite to a benign one (damage pre-emption) # Prevent damage from happening by limiting the build-up of reactive, but non-damaged metabolites that can lead to harmful products (directed overflow) Damage-control systems can involve one or more specific enzymes. Types of damage Similarly to DNA and proteins, metabolites are prone to damage, which can occur chemically or through enzyme promiscuity. Much less is known about metabo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme Promiscuity
Enzyme promiscuity is the ability of an enzyme to catalyse a fortuitous side reaction in addition to its main reaction. Although enzymes are remarkably specific catalysts, they can often perform side reactions in addition to their main, native catalytic activity. These promiscuous activities are usually slow relative to the main activity and are under neutral selection. Despite ordinarily being physiologically irrelevant, under new selective pressures these activities may confer a fitness benefit therefore prompting the evolution of the formerly promiscuous activity to become the new main activity. An example of this is the atrazine chlorohydrolase (''atzA'' encoded) from '' Pseudomonas sp.'' ADP that evolved from melamine deaminase (''triA'' encoded), which has very small promiscuous activity toward atrazine, a man-made chemical. Introduction Enzymes are evolved to catalyse a particular reaction on a particular substrate with a high catalytic efficiency (''kcat/KM'', ''cf''. Michae ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glutamic Acid
Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can synthesize enough for its use. It is also the most abundant excitatory neurotransmitter in the vertebrate nervous system. It serves as the precursor for the synthesis of the inhibitory gamma-aminobutyric acid (GABA) in GABA-ergic neurons. Its molecular formula is . Glutamic acid exists in three optically isomeric forms; the dextrorotatory -form is usually obtained by hydrolysis of gluten or from the waste waters of beet-sugar manufacture or by fermentation.Webster's Third New International Dictionary of the English Language Unabridged, Third Edition, 1971. Its molecular structure could be idealized as HOOC−CH()−()2−COOH, with two carboxyl groups −COOH and one amino group −. However, in the solid state and mildly acidic water solutio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
L2HGDH
L-2-hydroxyglutarate dehydrogenase, mitochondrial is an enzyme that in humans is encoded by the ''L2HGDH'' gene, also known as C14orf160, on chromosome 14. Function This gene encodes L-2-hydroxyglutarate dehydrogenase, a flavin adenine dinucleotide (FAD)-dependent enzyme that oxidizes Alpha-Hydroxyglutaric acid, L-2-hydroxyglutarate to alpha-ketoglutarate in a variety of mammalian tissues. Mutations in this gene cause L-2-hydroxyglutaric aciduria, a rare autosomal recessive neurometabolic disorder resulting in moderate to severe mental retardation. L2HGDH codes for a protein that is 50 kDa in size. The L2HGDH protein contains a mitochondrial-targeting transit peptide and is localized to the mitochondrial inner membrane inside mitochondria inside the cell. The L2HGDH protein catalyzes the following reaction, and requires flavin adenine dinucleotide (FAD) as a Cofactor (biochemistry), co-factor: (S)-2-hydroxyglutarate + acceptor = 2-oxoglutarate + reduced acceptor. L-2-hydrox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maillard Reaction
The Maillard reaction ( ; ) is a chemical reaction between amino acids and reducing sugars that gives browned food its distinctive flavor. Seared steaks, fried dumplings, cookies and other kinds of biscuits, breads, toasted marshmallows, and many other foods undergo this reaction. It is named after French chemist Louis Camille Maillard, who first described it in 1912 while attempting to reproduce biological protein synthesis. The reaction is a form of non-enzymatic browning which typically proceeds rapidly from around . Many recipes call for an oven temperature high enough to ensure that a Maillard reaction occurs. At higher temperatures, caramelization (the browning of sugars, a distinct process) and subsequently pyrolysis (final breakdown leading to burning and the development of acrid flavors) become more pronounced. The reactive carbonyl group of the sugar reacts with the nucleophilic amino group of the amino acid and forms a complex mixture of poorly characterized molecules ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphoribosylamine
Phosphoribosylamine (PRA) is a biochemical intermediate in the formation of purine nucleotides via inosine-5-monophosphate, and hence is a building block for DNA and RNA. The vitamins thiamine and cobalamin also contain fragments derived from PRA. : It is the product of the enzyme amidophosphoribosyltransferase which attaches ammonia from glutamine to phosphoribosyl pyrophosphate (PRPP) at its anomeric carbon: : + → + + PPi The biosynthesis pathway next combines PRA with glycine in a process driven by ATP giving glycineamide ribonucleotide (GAR). The enzyme phosphoribosylamine—glycine ligase catalyses the reaction forming an amide bond: : + + ATP → + ADP + Pi See also * 5-Aminoimidazole ribotide * Purine metabolism Purine metabolism refers to the metabolic pathways to synthesize and break down purines that are present in many organisms. Biosynthesis Purines are biologically synthesized as nucleotides and in particular as ribotides, i.e. bases attached to r ... ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Riboflavin
Riboflavin, also known as vitamin B2, is a vitamin found in food and sold as a dietary supplement. It is essential to the formation of two major coenzymes, flavin mononucleotide and flavin adenine dinucleotide. These coenzymes are involved in energy metabolism, cellular respiration, and antibody production, as well as normal growth and development. The coenzymes are also required for the metabolism of niacin, vitamin B6, and folate. Riboflavin is prescribed to treat corneal thinning, and taken orally, may reduce the incidence of migraine headaches in adults. Riboflavin deficiency is rare and is usually accompanied by deficiencies of other vitamins and nutrients. It may be prevented or treated by oral supplements or by injections. As a water-soluble vitamin, any riboflavin consumed in excess of nutritional requirements is not stored; it is either not absorbed or is absorbed and quickly excreted in urine, causing the urine to have a bright yellow tint. Natural sources of rib ... [...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 photosynthesis, photosynthetic organisms to fuel, energy-rich molecules such as glucose. In chemical terms, it catalysis, 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 biology, biologically because it catalyzes the primary chemical reaction by which Total inorganic carbon, inorganic carbon enters the biosphere. While many autotrophic bacteria and archaea fix carbon via the reductive acetyl CoA Pathway, reductive acetyl CoA pathway, the 3-hydroxypropionate cycle, or the reverse Krebs cycle, these pathways are relatively small contributors to global carbon fixation compared t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reactive Intermediate
In chemistry, a reactive intermediate or an intermediate is a short-lived, high-energy, highly reactive molecule. When generated in a chemical reaction, it will quickly convert into a more stable molecule. Only in exceptional cases can these compounds be isolated and stored, e.g. low temperatures, matrix isolation. When their existence is indicated, reactive intermediates can help explain how a chemical reaction takes place. Most chemical reactions take more than one elementary step to complete, and a reactive intermediate is a high-energy, yet stable, product that exists only in one of the intermediate steps. The series of steps together make a reaction mechanism. A reactive intermediate differs from a reactant or product or a simple reaction intermediate only in that it cannot usually be isolated but is sometimes observable only through fast spectroscopic methods. It is stable in the sense that an elementary reaction forms the reactive intermediate and the elementary reaction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
L-2-hydroxyglutarate Dehydrogenase
In enzymology, an L-2-hydroxyglutarate dehydrogenase () is an enzyme that catalyzes the chemical reaction :(S)-2-hydroxyglutarate + acceptor \rightleftharpoons 2-oxoglutarate + reduced acceptor Thus, the two substrates of this enzyme are (S)-2-hydroxyglutarate and acceptor, whereas its two products are 2-oxoglutarate and reduced acceptor. Enzymes which preferentially catalyze the conversion of the (R) stereoisomer of 2-oxoglutarate also exist in both mammals and plants and are named D-2-hydroxyglutarate dehydrogenase. L-2-hydroxyglutarate is produced by promiscuous action of malate dehydrogenase on 2-oxoglutarate; L-2-hydroxyglutarate dehydrogenase is an example of a metabolite repair enzyme that oxidizes L-2-hydroxyglutarate back to 2-oxoglutarate. Nomenclature This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with other acceptors. The systematic name of this enzyme class is (S)-2-hydroxyglutarate:acceptor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2-Hydroxyglutaric Aciduria
2-hydroxyglutaric aciduria is a rare neurometabolic disorder characterized by the significantly elevated levels of hydroxyglutaric acid in one's urine. It is either autosomal recessive or autosomal dominant. Presentation The signs/symptoms of this condition are consistent with the following: *Intellectual disability, *Muscular hypotonia *Encephalitis *Seizures *Aphasia Cause Mutation in several genes can lead to different types of 2-hydroxyglutaric aciduria. For example, the D2HGDH and L2HGDH genes provide instructions for making enzymes that are found in mitochondria - in which these enzymes break down D-2-hydroxyglutarate and L-2-hydroxyglutarate, respectively, as a part of normal reaction series that generate energy for cell activities. Any mutations occur in either of these genes would interrupt the functional enzymes and allow both 2-hydroxyglutarates to accumulate in cells, which cause 2-hydroxyglutaric aciduria type I. Moreover, it is known that type II for L-2-hydroxygl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme Promiscuity
Enzyme promiscuity is the ability of an enzyme to catalyse a fortuitous side reaction in addition to its main reaction. Although enzymes are remarkably specific catalysts, they can often perform side reactions in addition to their main, native catalytic activity. These promiscuous activities are usually slow relative to the main activity and are under neutral selection. Despite ordinarily being physiologically irrelevant, under new selective pressures these activities may confer a fitness benefit therefore prompting the evolution of the formerly promiscuous activity to become the new main activity. An example of this is the atrazine chlorohydrolase (''atzA'' encoded) from '' Pseudomonas sp.'' ADP that evolved from melamine deaminase (''triA'' encoded), which has very small promiscuous activity toward atrazine, a man-made chemical. Introduction Enzymes are evolved to catalyse a particular reaction on a particular substrate with a high catalytic efficiency (''kcat/KM'', ''cf''. Michae ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
