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GTP Cyclohydrolase
GTP cyclohydrolases are enzymes that catalyze imidazole ring opening of guanosine triphosphate (GTP). This reaction is the committed step in the biosynthesis of multiple coenzymes (such as riboflavin and folate), tRNA bases, and the phytotoxin toxoflavin. Several GTP cyclohydrolases exist, which sometimes synthesize different products for different pruposes: * GTP cyclohydrolase I, part of the tetrahydrobiopterin, tetrahydrofolate, queuosine and other biosynthetic pathways * GTP cyclohydrolase Ia, * GTP cyclohydrolase Ib, part of the tetrahydrobiopterin, tetrahydrofolate, queueosine and other biosynthetic pathways * GTP cyclohydrolase II, part of the riboflavin and toxoflavin biosynthetic pathways * GTP cyclohydrolase IIa (or GTP cyclohydrolase III{{Cite web , title=ENZYME - 3.5.4.29 GTP cyclohydrolase IIa , url=https://enzyme.expasy.org/EC/3.5.4.29 , access-date=2023-01-23 , website=enzyme.expasy.org), part of the riboflavin and deazaflavin cofactor biosynthetic pathways * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrahydrofolate
Tetrahydrofolic acid (THFA), or tetrahydrofolate, is a folic acid derivative. Metabolism Human synthesis Tetrahydrofolic acid is produced from dihydrofolic acid by dihydrofolate reductase. This reaction is inhibited by methotrexate. It is converted into 5,10-methylenetetrahydrofolate by serine hydroxymethyltransferase. Bacterial synthesis Many bacteria use dihydropteroate synthetase to produce dihydropteroate, a molecule without function in humans. This makes it a useful target for sulfonamide antibiotics, which compete with the PABA precursor. Functions Tetrahydrofolic acid is a cofactor in many reactions, especially in the synthesis (or anabolism) of amino acids and nucleic acids. In addition, it serves as a carrier molecule for single-carbon moieties, that is, groups containing one carbon atom e.g. methyl, methylene, methenyl, formyl, or formimino. When combined with one such single-carbon moiety as in 10-formyltetrahydrofolate, it acts as a donor of a group ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cations
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convention. The net charge of an ion is not zero because its total number of electrons is unequal to its total number of protons. A cation is a positively charged ion with fewer electrons than protons while an anion is a negatively charged ion with more electrons than protons. Opposite electric charges are pulled towards one another by electrostatic force, so cations and anions attract each other and readily form ionic compounds. Ions consisting of only a single atom are termed atomic or monatomic ions, while two or more atoms form molecular ions or polyatomic ions. In the case of physical ionization in a fluid (gas or liquid), "ion pairs" are created by spontaneous molecule collisions, where each generated pair consists of a free electron and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deazaflavin
Coenzyme F420 or 8-hydroxy-5-deazaflavin is a coenzyme (sometimes called a cofactor) involved in redox reactions in methanogens, in many Actinomycetota, and sporadically in other bacterial lineages. It is a flavin derivative. The coenzyme is a substrate for coenzyme F420 hydrogenase, 5,10-methylenetetrahydromethanopterin reductase and methylenetetrahydromethanopterin dehydrogenase. A particularly rich natural source of F420 is ''Mycobacterium smegmatis'', in which several dozen enzymes use F420 instead of the related cofactor FMN used by homologous enzymes in most other species. Eukaryotes including the fruit fly ''Drosophila melanogaster'' and the algae ''Ostreococcus tauri'' also use a precursor to this cofactor. Biosynthesis Coenzyme F420 is synthesized via a multi-step pathway: * 7,8-didemethyl-8-hydroxy-5-deazariboflavin synthase produces Coenzyme FO (also written F0), itself a cofactor of DNA photolyase (antenna). This is the head portion of the molecule. * 2-phos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GTP Cyclohydrolase IIa
In enzymology, a GTP cyclohydrolase IIa () is an enzyme that catalyzes the chemical reaction :GTP + 3 H2O \rightleftharpoons 2-amino-5-formylamino-6-(5-phosphoribosylamino)pyrimidin-4(3H)-one + 2 phosphate Thus, the two substrates of this enzyme are GTP and H2O, whereas its two products are 2-amino-5-formylamino-6-(5-phosphoribosylamino)pyrimidin-4(3H)-one and 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 phospho .... This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in cyclic amidines. The systematic name of this enzyme class is GTP 8,9-hydrolase (phosphate-forming). References * EC 3.5.4 Enzymes of unknown structure {{3.5-enzyme-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GTP Cyclohydrolase II
In enzymology, a GTP cyclohydrolase II () is an enzyme that catalyzes the chemical reaction :GTP + 3 H2O \rightleftharpoons formate + 2,5-diamino-6-hydroxy-4-(5-phosphoribosylamino)pyrimidine + diphosphate Thus, the two substrates of this enzyme are GTP and H2O, whereas its 3 products are formate, 2,5-diamino-6-hydroxy-4-(5-phosphoribosylamino)pyrimidine, and diphosphate. This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in cyclic amidines. The systematic name of this enzyme class is GTP 7,8-8,9-dihydrolase (diphosphate-forming). Other names in common use include guanosine triphosphate cyclohydrolase II, and GTP-8-formylhydrolase. This enzyme participates in riboflavin metabolism 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. Thes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Queuosine
Queuosine is a modified nucleoside that is present in certain tRNAs in bacteria and eukaryotes. It contains the nucleobase queuine. Originally identified in ''Escherichia coli, E. coli'', queuosine was found to occupy the first anticodon position of tRNAs for histidine, aspartic acid, asparagine and tyrosine. The first anticodon position pairs with the third "wobble base pair, wobble" position in codons, and queuosine improves accuracy of Translation (biology), translation compared to guanosine. Synthesis of queuosine begins with guanosine triphosphate, GTP. In bacteria, three structurally unrelated classes of riboswitch are known to regulate genes that are involved in the synthesis or transport of pre-queuosine1, a precursor to queuosine: PreQ1 riboswitch, PreQ1-I riboswitches, PreQ1-II riboswitches and PreQ1-III riboswitches. Queuosine biosynthesis genes have also been found on phage genomes and may be involved in protection from genome degradation by the host. References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrahydrobiopterin
Tetrahydrobiopterin (BH4, THB), also known as sapropterin (INN), is a cofactor of the three aromatic amino acid hydroxylase enzymes, used in the degradation of amino acid phenylalanine and in the biosynthesis of the neurotransmitters serotonin (5-hydroxytryptamine, 5-HT), melatonin, dopamine, norepinephrine (noradrenaline), epinephrine (adrenaline), and is a cofactor for the production of nitric oxide (NO) by the nitric oxide synthases. Chemically, its structure is that of a (dihydropteridine reductase) reduced pteridine derivative (quinonoid dihydrobiopterin). Medical use Tetrahydrobiopterin is available as a tablet for oral administration in the form of ''sapropterin dihydrochloride'' (BH4*2HCL). It was approved for use in the United States as a tablet in December 2007 and as a powder in December 2013. It was approved for use in the European Union in December 2008, Canada in April 2010, and Japan in July 2008. It is sold under the brand names Kuvan and Biopten. The typica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
