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IUPAC name 1-(4-Aminobutyl)guanidine [1] | |
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ChemSpider | |
ECHA InfoCard | 100.005.626 |
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KEGG | |
MeSH | Agmatine |
PubChem CID | |
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CompTox Dashboard (EPA) | |
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Properties | |
C5H14N4 | |
Molar mass | 130.195 g·mol−1 |
Density | 1.2 g/ml |
Melting point | 102 °C (216 °F; 375 K) |
Boiling point | 281 °C (538 °F; 554 K) |
high | |
log P | −1.423 |
Basicity (pKb) | 0.52 |
Hazards | |
Flash point | 95.8 °C (204.4 °F; 368.9 K) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Agmatine, also known as 4-aminobutyl-guanidine, was discovered in 1910 by Albrecht Kossel. [2] It is a chemical substance which is naturally created from the amino acid arginine. Agmatine has been shown to exert modulatory action at multiple molecular targets, notably: neurotransmitter systems, ion channels, nitric oxide (NO) synthesis, and polyamine metabolism and this provides bases for further research into potential applications.
The term agmatine stems from A- (for amino-) + g- (from guanidine) + -ma- (from ptomaine) + -in (German)/-ine (English) suffix with insertion of -t- apparently for euphony. [3] A year after its discovery, it was found that agmatine could increase blood flow in rabbits; [4] however, the physiological relevance of these findings were questioned given the high concentrations (high μM range) required. [5] In the 1920s, researchers in the diabetes clinic of Oskar Minkowski showed that agmatine can exert mild hypoglycemic effects. [6] In 1994, endogenous agmatine synthesis in mammals was discovered. [7]
Agmatine is a cationic amine formed by decarboxylation of L-arginine by the mitochondrial enzyme arginine decarboxylase (ADC). [8] Agmatine degradation occurs mainly by hydrolysis, catalyzed by agmatinase into urea and putrescine, the diamine precursor of polyamine biosynthesis. [9] An alternative pathway, mainly in peripheral tissues, is by diamine oxidase-catalyzed oxidation into agmatine-aldehyde, which is in turn converted by aldehyde dehydrogenase into guanidinobutyrate and secreted by the kidneys. [10]
Agmatine was found to exert modulatory actions directly and indirectly at multiple key molecular targets underlying cellular control mechanisms of cardinal importance in health and disease. It is considered capable of exerting its modulatory actions simultaneously at multiple targets. [11] The following outline indicates the categories of control mechanisms, and identifies their molecular targets:
Agmatine sulfate injection can increase food intake with carbohydrate preference in satiated, but not hungry, rats and this effect may be mediated by neuropeptide Y. [15] However, supplementation in rat drinking water results in slight reductions in water intake, body weight, and blood pressure. [16] In addition, force feeding with agmatine leads to a reduction in body weight gain during rat development. [17] It is also found that many fermented foods contain agmatine. [18] [19]
Agmatine is present in small amounts in plant-, animal-, and fish-derived foodstuff and gut microbial production is an added source for agmatine. Oral agmatine is absorbed from the gastrointestinal tract and readily distributed throughout the body. [20] Rapid elimination from non-brain organs of ingested (un-metabolized) agmatine by the kidneys has indicated a blood half life of about 2 hours. [21]
A number of potential medical uses for agmatine have been suggested. [22]
Agmatine produces mild reductions in heart rate and blood pressure, apparently by activating both central and peripheral control systems via modulation of several of its molecular targets including: imidazoline receptors subtypes, norepinephrine release and NO production. [23]
Agmatine hypoglycemic effects are the result of simultaneous modulation of several molecular mechanisms involved in blood glucose regulation. [11]
Agmatine has been shown to enhance glomerular filtration rate (GFR) and to exert nephroprotective effects. [24]
Agmatine has been discussed as a putative neurotransmitter. It is synthesized in the brain, stored in synaptic vesicles, accumulated by uptake, released by membrane depolarization, and inactivated by agmatinase. Agmatine binds to α2-adrenergic receptor and imidazoline receptor binding sites, and blocks NMDA receptors and other cation ligand-gated channels. However, while agmatine binds to α2-adrenergic receptors, it exerts neither an agonistic nor antagonistic effect on these receptors, lacking any intrinsic activity. [25] [26] Short only of identifying specific ("own") post-synaptic receptors, agmatine fulfills Henry Dale's criteria for a neurotransmitter and is hence considered a neuromodulator and co-transmitter. The existence of theoretical agmatinergic-mediated neuronal systems has not yet been demonstrated although the existence of such receptors is implied by its prominence in the mediation of both the central and peripheral nervous systems. [11] Research into agmatine-specific receptors and transmission pathways continues.
Due to its ability to pass through open cationic channels, agmatine has also been used as a surrogate metric of integrated ionic flux into neural tissue upon stimulation. [27] When neural tissue is incubated in agmatine and an external stimulus is applied, only cells with open channels will be filled with agmatine, allowing identification of which cells are sensitive to that stimuli and the degree to which they opened their cationic channels during the stimulation period.
Systemic agmatine can potentiate opioid analgesia, and prevent tolerance to chronic morphine in laboratory rodents. Since then, cumulative evidence amply shows that agmatine inhibits opioid dependence and relapse in several animal species. [28]
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell.
Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) and both the amino and guanidino groups are protonated, resulting in a cation. Only the l-arginine (symbol Arg or R) enantiomer is found naturally. Arg residues are common components of proteins. It is encoded by the codons CGU, CGC, CGA, CGG, AGA, and AGG. The guanidine group in arginine is the precursor for the biosynthesis of nitric oxide. Like all amino acids, it is a white, water-soluble solid.
The N-methyl-D-aspartatereceptor (also known as the NMDA receptor or NMDAR), is a glutamate receptor and predominantly Ca2+ ion channel found in neurons. The NMDA receptor is one of three types of ionotropic glutamate receptors, the other two being AMPA and kainate receptors. Depending on its subunit composition, its ligands are glutamate and glycine (or D-serine). However, the binding of the ligands is typically not sufficient to open the channel as it may be blocked by Mg2+ ions which are only removed when the neuron is sufficiently depolarized. Thus, the channel acts as a "coincidence detector" and only once both of these conditions are met, the channel opens and it allows positively charged ions (cations) to flow through the cell membrane. The NMDA receptor is thought to be very important for controlling synaptic plasticity and mediating learning and memory functions.
Vasodilation, also known as vasorelaxation, is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. Blood vessel walls are composed of endothelial tissue and a basal membrane lining the lumen of the vessel, concentric smooth muscle layers on top of endothelial tissue, and an adventitia over the smooth muscle layers. Relaxation of the smooth muscle layer allows the blood vessel to dilate, as it is held in a semi-constricted state by sympathetic nervous system activity. Vasodilation is the opposite of vasoconstriction, which is the narrowing of blood vessels.
An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agonist, while an inverse agonist causes an action opposite to that of the agonist.
A biogenic amine is a biogenic substance with one or more amine groups. They are basic nitrogenous compounds formed mainly by decarboxylation of amino acids or by amination and transamination of aldehydes and ketones. Biogenic amines are organic bases with low molecular weight and are synthesized by microbial, vegetable and animal metabolisms. In food and beverages they are formed by the enzymes of raw material or are generated by microbial decarboxylation of amino acids.
Nitric oxide synthases (NOSs) are a family of enzymes catalyzing the production of nitric oxide (NO) from L-arginine. NO is an important cellular signaling molecule. It helps modulate vascular tone, insulin secretion, airway tone, and peristalsis, and is involved in angiogenesis and neural development. It may function as a retrograde neurotransmitter. Nitric oxide is mediated in mammals by the calcium-calmodulin controlled isoenzymes eNOS and nNOS. The inducible isoform, iNOS, involved in immune response, binds calmodulin at physiologically relevant concentrations, and produces NO as an immune defense mechanism, as NO is a free radical with an unpaired electron. It is the proximate cause of septic shock and may function in autoimmune disease.
Spermidine is a polyamine compound found in ribosomes and living tissues and having various metabolic functions within organisms.
Gasotransmitters is a class of neurotransmitters. The molecules are distinguished from other bioactive endogenous gaseous signaling molecules based on a need to meet distinct characterization criteria. Currently, only nitric oxide, carbon monoxide, and hydrogen sulfide are accepted as gasotransmitters. According to in vitro models, gasotransmitters, like other gaseous signaling molecules, may bind to gasoreceptors and trigger signaling in the cells.
Clorgiline (INN), or clorgyline (BAN), is a monoamine oxidase inhibitor (MAOI) structurally related to pargyline which is described as an antidepressant. Specifically, it is an irreversible and selective inhibitor of monoamine oxidase A (MAO-A). Clorgiline was never marketed, but it has found use in scientific research. It has been found to bind with high affinity to the σ1 receptor (Ki = 3.2 nM) and with very high affinity to the I2 imidazoline receptor (Ki = 40 pM).
The 5-HT3 receptor belongs to the Cys-loop superfamily of ligand-gated ion channels (LGICs) and therefore differs structurally and functionally from all other 5-HT receptors (5-hydroxytryptamine, or serotonin receptors) which are G protein-coupled receptors. This ion channel is cation-selective and mediates neuronal depolarization and excitation within the central and peripheral nervous systems.
Imidazoline receptors are the primary receptors on which clonidine and other imidazolines act. There are three main classes of imidazoline receptor: I1 is involved in inhibition of the sympathetic nervous system to lower blood pressure, I2 has as yet uncertain functions but is implicated in several psychiatric conditions, and I3 regulates insulin secretion.
7-Nitroindazole, or 7-NI, is a heterocyclic small molecule containing an indazole ring that has been nitrated at the 7 position. Nitroindazole acts as a selective inhibitor for neuronal nitric oxide synthase, a hemoprotein enzyme that, in neuronal tissue, converts arginine to citrulline and nitric oxide (NO). Nitric oxide can diffuse through the plasma membrane into neighbouring cells, allowing cell signalling, so nitroindazole indirectly inhibits this signalling process. Other inhibitors exist such as 3-bromo-7-nitroindazole, which is more potent but less specific, or N-propyl-L-arginine (NPA), which acts on a different site.
Biological functions of nitric oxide are roles that nitric oxide plays within biology.
A ureohydrolase is a type of hydrolase enzyme. The ureohydrolase superfamily includes arginase, agmatinase, formiminoglutamase and proclavaminate amidinohydrolase. These enzymes share a 3-layer alpha-beta-alpha structure, and play important roles in arginine/agmatine metabolism, the urea cycle, histidine degradation, and other pathways.
Dihydroalprenolol (DHA) is a hydrogenated alprenolol derivative that acts as a beta-adrenergic blocker. When the extra hydrogen atoms are tritium, it is a radiolabeled form of alprenolol, which is used to label beta-adrenergic receptors for isolation.
Nitroarginine, or Nω-nitro-l-arginine, also known as L-NOARG, is a nitro derivative of the amino acid arginine. It is an inhibitor of nitric oxide synthase and hence a vasoconstrictor. As such, it finds widespread use as a biochemical tool in the study of nitric oxide and its biological effects.
Aganodine is a guanidine that activates presynaptic imidazoline receptors. Through its agonism at imidazoline receptors, aganodine inhibits the presynaptic release of norepinephrine.
Gaseous signaling molecules are gaseous molecules that are either synthesized internally (endogenously) in the organism, tissue or cell or are received by the organism, tissue or cell from outside and that are used to transmit chemical signals which induce certain physiological or biochemical changes in the organism, tissue or cell. The term is applied to, for example, oxygen, carbon dioxide, sulfur dioxide, nitrous oxide, hydrogen cyanide, ammonia, methane, hydrogen, ethylene, etc.
In neuroscience, glutamate is the anion of glutamic acid in its role as a neurotransmitter. It is by a wide margin the most abundant excitatory neurotransmitter in the vertebrate nervous system. It is used by every major excitatory function in the vertebrate brain, accounting in total for well over 90% of the synaptic connections in the human brain. It also serves as the primary neurotransmitter for some localized brain regions, such as cerebellum granule cells.