Adenosine monophosphate

Adenosine monophosphate (AMP), also known as 5'-adenylic acid, is a nucleotide. AMP consists of a phosphate group, the sugar ribose, and the nucleobase adenine; it is an ester of phosphoric acid and the nucleoside adenosine.[1] As a substituent it takes the form of the prefix adenylyl-.[2]

Adenosine monophosphate
Names
IUPAC name
[(2R,3S,4R,5R)-5-(6-aminopurin-9-yl)-3,4-dihydroxyoxolan-2-yl]methyl dihydrogen phosphate
Other names
Adenosine 5'-monophosphate, 5'-Adenylic acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.455
KEGG
MeSH Adenosine+monophosphate
UNII
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, 3.8, 6.1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

AMP plays an important role in many cellular metabolic processes, being interconverted to ADP and/or ATP. AMP is also a component in the synthesis of RNA.[3]

Production and degradation

AMP does not have the high energy phosphoanhydride bond associated with ADP and ATP. AMP can be produced from ADP:

2 ADP → ATP + AMP

Or AMP may be produced by the hydrolysis of one high energy phosphate bond of ADP:

ADP + H2O → AMP + Pi

AMP can also be formed by hydrolysis of ATP into AMP and pyrophosphate:

ATP + H2O → AMP + PPi

When RNA is broken down by living systems, nucleoside monophosphates, including adenosine monophosphate, are formed.

AMP can be regenerated to ATP as follows:

AMP + ATP → 2 ADP (adenylate kinase in the opposite direction)
ADP + Pi → ATP (this step is most often performed in aerobes by the ATP synthase during oxidative phosphorylation)

AMP can be converted into IMP by the enzyme myoadenylate deaminase, freeing an ammonia group.

In a catabolic pathway, adenosine monophosphate can be converted to uric acid, which is excreted from the body in mammals.[4]

Physiological role in regulation

AMP-activated kinase regulation

The eukaryotic cell enzyme 5' adenosine monophosphate-activated protein kinase, or AMPK, utilizes AMP for homeostatic energy processes during times of high cellular energy expenditure, such as exercise.[5] Since ATP cleavage, and corresponding phosphorylation 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.[6]

Though phosphorylation appears to be the main activator for AMPK, some studies suggest that AMP is an allosteric regulator as well as a direct agonist for AMPK.[7] Furthermore, other studies suggest that the high ratio of AMP:ATP levels in cells, rather than just AMP, activate AMPK.[8] For example, the species of Caenorhabditis elegans and Drosophila melanogaster and their AMP-activated kinases were found to have been activated by AMP, while species of yeast and plant kinases were not allosterically activated by AMP.[8]

AMP binds to the γ-subunit of AMPK, leading to the activation of the kinase, and then eventually a cascade of other processes such as the activation of catabolic pathways and inhibition of anabolic 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.[9] Though the γ-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 the dephosphorylation state for the enzyme.[10] The dephosphorylation of AMPK through various protein phosphatases completely inactivates catalytic function. AMP/ADP protects AMPK from being inactivated by binding to the γ-subunit and maintaining the dephosphorylation state.[11]

cAMP

AMP can also exist as a cyclic structure known as cyclic AMP (or cAMP). Within certain cells the enzyme adenylate cyclase makes cAMP from ATP, and typically this reaction is regulated by hormones such as adrenaline or glucagon. cAMP plays an important role in intracellular signaling.[12]

See also

References
  1. "Adenosine monophosphate (Compound)". PubChem. NCBI. Retrieved 30 April 2020.
  2. "Nomenclature of Carbohydrates: (Recommendations 1996)". Journal of Carbohydrate Chemistry. 16 (8): 1191–1280. 1997. doi:10.1080/07328309708005748.
  3. Jauker M, Griesser H, Richert C (November 2015). "Spontaneous Formation of RNA Strands, Peptidyl RNA, and Cofactors". Angewandte Chemie. 54 (48): 14564–9. doi:10.1002/anie.201506593. PMC 4678511. PMID 26435376.
  4. Maiuolo J, Oppedisano F, Gratteri S, Muscoli C, Mollace V (June 2016). "Regulation of uric acid metabolism and excretion". International Journal of Cardiology. 213: 8–14. doi:10.1016/j.ijcard.2015.08.109. PMID 26316329.
  5. Richter EA, Ruderman NB (March 2009). "AMPK and the biochemistry of exercise: implications for human health and disease". The Biochemical Journal. 418 (2): 261–75. doi:10.1042/BJ20082055. PMC 2779044. PMID 19196246.
  6. Carling D, Mayer FV, Sanders MJ, Gamblin SJ (July 2011). "AMP-activated protein kinase: nature's energy sensor". Nature Chemical Biology. 7 (8): 512–8. doi:10.1038/nchembio.610. PMID 21769098.
  7. Faubert B, Vincent EE, Poffenberger MC, Jones RG (January 2015). "The AMP-activated protein kinase (AMPK) and cancer: many faces of a metabolic regulator". Cancer Letters. 356 (2 Pt A): 165–70. doi:10.1016/j.canlet.2014.01.018. PMID 24486219.
  8. Hardie DG (15 September 2011). "AMP-activated protein kinase—an energy sensor that regulates all aspects of cell function". Genes & Development. 25 (18): 1895–1908. doi:10.1101/gad.17420111. ISSN 0890-9369. PMC 3185962. PMID 21937710.
  9. Hardie DG (February 2011). "Energy sensing by the AMP-activated protein kinase and its effects on muscle metabolism". The Proceedings of the Nutrition Society. 70 (1): 92–9. doi:10.1017/S0029665110003915. PMID 21067629.
  10. Krishan S, Richardson DR, Sahni S (March 2015). "Adenosine monophosphate-activated kinase and its key role in catabolism: structure, regulation, biological activity, and pharmacological activation". Molecular Pharmacology. 87 (3): 363–77. doi:10.1124/mol.114.095810. PMID 25422142.
  11. Xiao B, Sanders MJ, Underwood E, Heath R, Mayer FV, Carmena D, Jing C, Walker PA, Eccleston JF, Haire LF, Saiu P, Howell SA, Aasland R, Martin SR, Carling D, Gamblin SJ (April 2011). "Structure of mammalian AMPK and its regulation by ADP". Nature. 472 (7342): 230–3. doi:10.1038/nature09932. PMC 3078618. PMID 21399626.
  12. Ravnskjaer K, Madiraju A, Montminy M (2015). Metabolic Control. Handbook of Experimental Pharmacology. 233. Springer, Cham. pp. 29–49. doi:10.1007/164_2015_32. ISBN 9783319298047. PMID 26721678.

Further reading
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