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| Names | |
|---|---|
| IUPAC name 5′-Adenylic acid | |
| Systematic IUPAC name [(2R,3S,4R,5R)-5-(6-Amino-9H-purin-9-yl)-3,4-dihydroxyoxolan-2-yl]methyl dihydrogen phosphate | |
| Other names Adenosine 5'-monophosphate Vitamin B8[1] | |
| Identifiers | |
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3D model (JSmol) | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
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| DrugBank |
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| ECHA InfoCard | 100.000.455 |
| KEGG |
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| MeSH | Adenosine+monophosphate |
| UNII | |
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| Properties | |
| C10H14N5O7P | |
| Molar mass | 347.22 g/mol |
| Appearance | white crystalline powder |
| Density | 2.32 g/mL |
| Melting point | 178 to 185 °C (352 to 365 °F; 451 to 458 K) |
| Boiling point | 798.5 °C (1,469.3 °F; 1,071.7 K) |
| Acidity (pKa) | 0.9[citation needed], 3.8, 6.1 |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Adenosine monophosphate (AMP),[2] also known as5'-adenylic acid, is anucleotide. AMP consists of aphosphate group, the sugarribose, and thenucleobaseadenine. It is anester ofphosphoric acid and thenucleosideadenosine.[3] As asubstituent it takes the form of the prefixadenylyl-.[4]
AMP plays an important role in many cellular metabolic processes, being interconverted toadenosine triphosphate (ATP) andadenosine diphosphate (ADP), as well asallosterically activating enzymes such as myophosphorylase-b. AMP is also a component in the synthesis ofRNA.[5] AMP is present in all known forms of life.[6]
AMP does not have the high energyphosphoanhydride bond associated with ADP and ATP. AMP can be produced fromADP by themyokinase (adenylate kinase) reaction when the ATP reservoir in the cell is low:[7][8]
Or AMP may be produced by thehydrolysis of onehigh energy phosphate bond of ADP:
AMP can also be formed by hydrolysis ofATP into AMP andpyrophosphate:
When RNA is broken down by living systems, nucleoside monophosphates, including adenosine monophosphate, are formed.
AMP can be regenerated to ATP as follows:
AMP can be converted intoinosine monophosphate by theenzymemyoadenylate deaminase, freeing anammonia group.
In acatabolic pathway, thepurine nucleotide cycle, adenosine monophosphate can be converted touric acid, which is excreted from the body in mammals.[9]
The eukaryotic cell enzyme5' adenosine monophosphate-activated protein kinase, or AMPK, utilizes AMP forhomeostatic energy processes during times of high cellular energy expenditure, such as exercise.[10] Since ATP cleavage, and correspondingphosphorylation reactions, are utilized in various processes throughout the body as a source of energy, ATP production is necessary to further create energy for those mammalian cells. AMPK, as a cellular energy sensor, is activated by decreasing levels of ATP, which is naturally accompanied by increasing levels of ADP and AMP.[11]
Though phosphorylation appears to be the mainactivator for AMPK, some studies suggest that AMP is anallosteric regulator as well as adirect agonist for AMPK.[12] Furthermore, other studies suggest that the high ratio of AMP:ATP levels in cells, rather than just AMP, activate AMPK.[13] For example, the AMP-activated kinases ofCaenorhabditis elegans andDrosophila melanogaster were found to have been activated by AMP, whileyeast and plant kinases were not allosterically activated by AMP.[13]
AMP binds to theγ-subunit of AMPK, leading to the activation of the kinase, and then eventually acascade of other processes such as the activation ofcatabolic pathways andinhibition ofanabolic pathways to regenerate ATP. Catabolic mechanisms, which generate ATP through the release of energy from breaking down molecules, are activated by the AMPK enzyme while anabolic mechanisms, which utilize energy from ATP to form products, are inhibited.[14] Though theγ-subunit can bind AMP/ADP/ATP, only the binding of AMP/ADP results in a conformational shift of the enzyme protein. This variance in AMP/ADP versus ATP binding leads to a shift in thedephosphorylation state for the enzyme.[15] The dephosphorylation of AMPK through various proteinphosphatases completely inactivates catalytic function. AMP/ADP protects AMPK from being inactivated by binding to theγ-subunit and maintaining the dephosphorylation state.[16]
AMP can also exist as a cyclic structure known ascyclic AMP (or cAMP). Within certain cells the enzymeadenylate cyclase makes cAMP from ATP, and typically this reaction is regulated by hormones such asadrenaline orglucagon. cAMP plays an important role in intracellular signaling.[17] In skeletal muscle, cyclic AMP, triggered by adrenaline, starts a cascade (cAMP-dependent pathway) for the conversion of myophosphorylase-b into the phosphorylated form ofmyophoshorylase-a for glycogenolysis.[18][19]
