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Adenosine monophosphate (AMP), also known as 5'-adenylic acid, is a
nucleotide Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecule ...
. AMP consists of a
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 phosph ...
group, the sugar ribose, and the nucleobase adenine; it is an ester of
phosphoric acid Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, w ...
and the
nucleoside Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group. A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar (ribose or 2'-deoxyribose) whereas a nucleoti ...
adenosine. As a substituent it takes the form of the prefix adenylyl-. 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. AMP is present in all known forms of life.


Production and degradation

AMP does not have the high energy
phosphoanhydride High-energy phosphate can mean one of two things: * The phosphate-phosphate (phosphoanhydride/phosphoric anhydride/macroergic/phosphagen) bonds formed when compounds such as adenosine diphosphate (ADP) and adenosine triphosphate (ATP) are created. ...
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 High-energy phosphate can mean one of two things: * The phosphate-phosphate (phosphoanhydride/phosphoric anhydride/macroergic/phosphagen) bonds formed when compounds such as adenosine diphosphate (ADP) and adenosine triphosphate (ATP) are created. ...
bond of ADP: : ADP + H2O → AMP + Pi AMP can also be formed by hydrolysis of ATP into AMP and
pyrophosphate In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a P–O–P linkage. A number of pyrophosphate salts exist, such as disodium pyrophosphate (Na2H2P2O7) and tetrasodium pyrophosphate (Na4P2O7), among othe ...
: : 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 Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
myoadenylate deaminase, freeing an
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
group. In a catabolic pathway, adenosine monophosphate can be converted to
uric acid Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates, such as ammonium acid urate. Uric acid is a product of the metabolic breakdown ...
, which is excreted from the body in mammals.


Physiological role in regulation


AMP-activated kinase regulation

The eukaryotic cell enzyme 5' adenosine monophosphate-activated protein kinase, or AMPK, utilizes AMP for
homeostatic In biology, homeostasis (British also homoeostasis) (/hɒmɪə(ʊ)ˈsteɪsɪs/) is the state of steady internal, physical, and chemical conditions maintained by living systems. This is the condition of optimal functioning for the organism and ...
energy processes during times of high cellular energy expenditure, such as exercise. 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. 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. Furthermore, other studies suggest that the high ratio of AMP:ATP levels in cells, rather than just AMP, activate AMPK. 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. 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. 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 In biochemistry, dephosphorylation is the removal of a phosphate (PO43−) group from an organic compound by hydrolysis. It is a reversible post-translational modification. Dephosphorylation and its counterpart, phosphorylation, activate and de ...
state for the enzyme. 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.


cAMP

AMP can also exist as a cyclic structure known as cyclic AMP (or cAMP). Within certain cells the enzyme
adenylate cyclase Adenylate cyclase (EC 4.6.1.1, also commonly known as adenyl cyclase and adenylyl cyclase, abbreviated AC) is an enzyme with systematic name ATP diphosphate-lyase (cyclizing; 3′,5′-cyclic-AMP-forming). It catalyzes the following reaction: :A ...
makes cAMP from ATP, and typically this reaction is regulated by hormones such as
adrenaline Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands an ...
or glucagon. cAMP plays an important role in intracellular signaling.


See also


References


Further reading

*


External links


GMD MS Spectrum
{{DEFAULTSORT:Adenosine phosphate1 Adenosine receptor agonists Neurotransmitters Nucleotides Phosphate esters Purines