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Acetolactate Synthase
The acetolactate synthase (ALS) enzyme (also known as acetohydroxy acid or acetohydroxyacid synthase, abbr. AHAS) is a protein found in plants and micro-organisms. ALS catalyzes the first step in the synthesis of the branched-chain amino acids (valine, leucine, and isoleucine). A human protein of yet unknown function, sharing some sequence similarity with bacterial ALS, is encoded by the ILVBL (ilvB-like) gene. Structure Gene Human ILVBL gene has 17 exons resides on chromosome 19 at q13.1. Protein The catalytic peptide of ALS in ''Arabidopsis thaliana'' (mouse-eared cress) is a chloroplastic protein consisting of 670 residues, the last 615 of which form the active form. Three main domains are found, with two thiamine pyrophosphate sandwiching a DHS-like NAD/FAD-binding domain. In SCOP assignment, these subunits are named d1yhya1, d1yhya2, and d1yhya3 from the N-terminal to the C-termianl. The structure of acetolactate synthase that was used for the picture on this page was d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arabidopsis Thaliana
''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land. A winter annual with a relatively short lifecycle, ''A. thaliana'' is a popular model organism in plant biology and genetics. For a complex multicellular eukaryote, ''A. thaliana'' has a relatively small genome around 135 megabase pairs. It was the first plant to have its genome sequenced, and is a popular tool for understanding the molecular biology of many plant traits, including flower development and light sensing. Description ''Arabidopsis thaliana'' is an annual (rarely biennial) plant, usually growing to 20–25 cm tall. The leaves form a rosette at the base of the plant, with a few leaves also on the flowering stem. The basal leaves are green to slightly purplish in color, 1.5–5 cm long, and 2–10 mm broad, with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nik Operon
The ''nik operon'' is an operon required for uptake of nickel ions into the cell. It is present in many bacteria, but has been extensively studied in ''Helicobacter pylori''. Nickel is an essential nutrient for many microorganisms, where it participates in a variety of cellular processes. However, excessive levels of nickel ions in cell can be fatal to the cell. Nickel ion concentration in the cell is regulated through the ''nik'' operon. Structure of the ''nik'' operon The ''nik'' operon consists of six genes. The first five genes ''nikABCDE'' encode components of a typical ABC transport system and the last gene ''nikR'' encodes a DNA-binding protein that represses transcription of ''nikABCDE'' when sufficient Ni2+ is present. The ''nikR'' gene is located 5 bp downstream of the end of ''nikE'', transcribed in the same direction as ''nikABCDE''. The following table summarizes the structure of the ''nik'' operon: Regulation ''nikR'' Regulation Regulation of expression of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amino Acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha amino acids appear in the genetic code. Amino acids can be classified according to the locations of the core structural functional groups, as Alpha and beta carbon, alpha- , beta- , gamma- or delta- amino acids; other categories relate to Chemical polarity, polarity, ionization, and side chain group type (aliphatic, Open-chain compound, acyclic, aromatic, containing hydroxyl or sulfur, etc.). In the form of proteins, amino acid '' residues'' form the second-largest component (water being the largest) of human muscles and other tissues. Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis. It is thought that they played a key role in enabling l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herbicide
Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page for EPA reports on pesticide use ihere Selective herbicides control specific weed species, while leaving the desired crop relatively unharmed, while non-selective herbicides (sometimes called total weedkillers in commercial products) can be used to clear waste ground, industrial and construction sites, railways and railway embankments as they kill all plant material with which they come into contact. Apart from selective/non-selective, other important distinctions include ''persistence'' (also known as ''residual action'': how long the product stays in place and remains active), ''means of uptake'' (whether it is absorbed by above-ground foliage only, through the roots, or by other means), and ''mechanism of action'' (how it works). Historic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme Inhibitor
An enzyme inhibitor is a molecule that binds to an enzyme and blocks its activity. Enzymes are proteins that speed up chemical reactions necessary for life, in which substrate molecules are converted into products. An enzyme facilitates a specific chemical reaction by binding the substrate to its active site, a specialized area on the enzyme that accelerates the most difficult step of the reaction. An enzyme inhibitor stops ("inhibits") this process, either by binding to the enzyme's active site (thus preventing the substrate itself from binding) or by binding to another site on the enzyme such that the enzyme's catalysis of the reaction is blocked. Enzyme inhibitors may bind reversibly or irreversibly. Irreversible inhibitors form a chemical bond with the enzyme such that the enzyme is inhibited until the chemical bond is broken. By contrast, reversible inhibitors bind non-covalently and may spontaneously leave the enzyme, allowing the enzyme to resume its function. Reve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leucine-responsive Protein
Leucine responsive protein, or Lrp, is a global regulator protein, meaning that it regulates the biosynthesis of leucine, as well as the other branched-chain amino acids, valine and isoleucine. In bacteria, it is encoded by the ''lrp'' gene. Lrp alternatively activates and represses the expression of acetolactate synthase's (ALS) several isoenzymes. Lrp, in E. coli, along with DAM plays a role in the regulation of the fim operon, a group of genes needed for successful synthesis and trafficking of Type I Pili. These hair like structures are important virulence factors for different pathogenic strains of Bacteria as they can mediate biofilm formation and adhesion to host epithelia. Other examples include Salmonella enterica serovar Typhimurium and Klebsiella pneumoniae ''Klebsiella pneumoniae'' is a Gram-negative, non-motile, encapsulated, lactose- fermenting, facultative anaerobic, rod-shaped bacterium. It appears as a mucoid lactose fermenter on MacConkey agar. Although f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketol-acid Reductoisomerase
In enzymology, a ketol-acid reductoisomerase () is an enzyme that catalyzes the chemical reaction :(R)-2,3-dihydroxy-3-methylbutanoate + NADP+ \rightleftharpoons (S)-2-hydroxy-2-methyl-3-oxobutanoate + NADPH + H+ Thus, the two substrates of this enzyme are (R)-2,3-dihydroxy-3-methylbutanoate and NADP+, whereas its 3 products are (S)-2-hydroxy-2-methyl-3-oxobutanoate, NADPH, and H+. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (R)-2,3-dihydroxy-3-methylbutanoate:NADP+ oxidoreductase (isomerizing). Other names in common use include dihydroxyisovalerate dehydrogenase (isomerizing), acetohydroxy acid isomeroreductase, ketol acid reductoisomerase, alpha-keto-beta-hydroxylacyl reductoisomerase, 2-hydroxy-3-keto acid reductoisomerase, acetohydroxy acid reductoisomerase, acetolactate reductoisomerase, dihydroxyisovalerate (isomerizing) dehydro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcription (biology)
Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs). mRNA comprises only 1–3% of total RNA samples. Less than 2% of the human genome can be transcribed into mRNA ( Human genome#Coding vs. noncoding DNA), while at least 80% of mammalian genomic DNA can be actively transcribed (in one or more types of cells), with the majority of this 80% considered to be ncRNA. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Transcription proceeds in the following general steps: # RNA polymerase, together with one or more general transcription factors, binds to promoter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcriptional Attenuation
In genetics, attenuation is a regulatory mechanism for some bacterial operons that results in premature termination of transcription. The canonical example of attenuation used in many introductory genetics textbooks, is ribosome-mediated attenuation of the ''trp'' operon. Ribosome-mediated attenuation of the ''trp'' operon relies on the fact that, in bacteria, transcription and translation proceed simultaneously. Attenuation involves a provisional stop signal (attenuator), located in the DNA segment that corresponds to the leader sequence of mRNA. During attenuation, the ribosome becomes stalled (delayed) in the attenuator region in the mRNA leader. Depending on the metabolic conditions, the attenuator either stops transcription at that point or allows read-through to the structural gene part of the mRNA and synthesis of the appropriate protein. Attenuation is a regulatory feature found throughout Archaea and Bacteria causing premature termination of transcription.Merino E, Yan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Threonine Ammonia-lyase
Threonine ammonia-lyase (EC 4.3.1.19, systematic name L-threonine ammonia-lyase (2-oxobutanoate-forming), also commonly referred to as threonine deaminase or threonine dehydratase, is an enzyme responsible for catalyzing the conversion of L-threonine into α-ketobutyrate and ammonia: :L-threonine = 2-oxobutanoate + NH3 (overall reaction) ::(1a) L-threonine = 2-aminobut-2-enoate + H2O ::(1b) 2-aminobut-2-enoate = 2-iminobutanoate (spontaneous) ::(1c) 2-iminobutanoate + H2O = 2-oxobutanoate + NH3 (spontaneous) α-Ketobutyrate can be converted into L-isoleucine, so threonine ammonia-lyase functions as a key enzyme in BCAA synthesis. It employs a pyridoxal-5'-phosphate cofactor, similar to many enzymes involved in amino acid metabolism. It is found in bacteria, yeast, and plants, though most research to date has focused on forms of the enzyme in bacteria. This enzyme was one of the first in which negative feedback inhibition by the end product of a metabolic pathway was directly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dihydroxy-acid Dehydratase
The enzyme dihydroxy-acid dehydratase () catalyzes the chemical reaction :2,3-dihydroxy-3-methylbutanoate \rightleftharpoons 3-methyl-2-oxobutanoate + H2O This enzyme participates in valine, leucine and isoleucine biosynthesis and pantothenate and coenzyme A (CoA) biosynthesis. Nomenclature This enzyme belongs to the family of lyases, specifically the hydro-lyases, which cleave carbon-oxygen bonds. The systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature. A semisystematic name or semitrivial ... of this enzyme class is 2,3-dihydroxy-3-methylbutanoate hydro-lyase (3-methyl-2-oxobutanoate-forming). Other names in common use include * acetohydroxyacid dehydratase, * α,β-dihydroxyacid dehydratase, * 2,3-dihydroxyisovalerate dehydratase, * α,β-dihydroxyisovalerate dehydratase, * dihydroxy acid dehydrase, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Branched-chain-amino-acid Transaminase
Branched-chain amino acid aminotransferase (BCAT), also known as branched-chain amino acid transaminase, is an aminotransferase enzyme which acts upon branched-chain amino acids (BCAAs). It is encoded by the ''BCAT2'' gene in humans. The BCAT enzyme catalyzes the conversion of BCAAs and α-ketoglutarate into branched chain α-keto acids and glutamate. The structure to the right of branched chain amino acid aminotransferase was found using X-ray diffraction with a resolution of 2.20 Å. The branched-chain amino acid aminotransferase found in this image was isolated from mycobacteria. This protein is made up of two identical polypeptide chains, totaling 372 residues. The biological function of branched-chain amino acid aminotransferases is to catalyse the synthesis or degradation of the branched chain amino acids leucine, isoleucine, and valine. In humans, branched chain amino acids are essential and are degraded by BCATs. Structure and function In humans, BCATs are homodim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
