Phosphorylation

{{Short description|Chemical process of introducing a phosphate}} [[File:Phosporylation of a serine residue, before and after shot.png|thumb|Serine in an amino acid chain, before and after phosphorylation.]]

In biochemistry, '''phosphorylation''' is described as the "transfer of a phosphate group" from a donor to an acceptor<ref name="ana&physio">{{cite journal |title=phosphorylation|url=https://goldbook.iupac.org/terms/view/PT06790|website=IUPAC Gold Book|date=2014 |doi=10.1351/goldbook.PT06790 |url-access=subscription}}</ref> or the addition of a phosphate group to a molecule. A common phosphorylating agent (phosphate donor) is ATP and a common family of acceptor are alcohols: :{{chem2|[Adenosyl\sO\sPO2\sO\sPO2\sO\sPO3](4-) + ROH -> Adenosyl\sO\sPO2\sO\sPO3H](2-) + [RO\sP\sO3](2-)}} This equation can be written in several ways that are nearly equivalent that describe the behaviors of various protonated states of ATP, ADP, and the phosphorylated product. As is clear from the equation, a phosphate group per se is not transferred, but a phosphoryl group (PO₃^-). '''Phosphoryl''' is an electrophile.<ref name=Ahn>{{cite journal |doi=10.1021/cr000230w |title=Kinetic and Catalytic Mechanisms of Protein Kinases |date=2001 |last1=Adams |first1=Joseph A. |journal=Chemical Reviews |volume=101 |issue=8 |pages=2271–2290 |pmid=11749373 }}</ref> This process and its inverse, dephosphorylation, are common in biology.<ref name="Chen-2022">{{cite journal |vauthors=Chen J, He X, Jakovlić I |date=November 2022 |title=Positive selection-driven fixation of a hominin-specific amino acid mutation related to dephosphorylation in IRF9 |journal=BMC Ecology and Evolution |volume=22 |issue=1 |article-number=132 |doi=10.1186/s12862-022-02088-5 |pmid=36357830 |pmc=9650800 |s2cid=253448972 |doi-access=free }} 50x50px Text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.</ref> Protein phosphorylation often activates (or deactivates) many enzymes.<ref>{{cite journal | vauthors = Oliveira AP, Sauer U | title = The importance of post-translational modifications in regulating Saccharomyces cerevisiae metabolism | journal = FEMS Yeast Research | volume = 12 | issue = 2 | pages = 104–117 | date = March 2012 | pmid = 22128902 | doi = 10.1111/j.1567-1364.2011.00765.x | doi-access = free }}</ref><ref>{{cite journal | vauthors = Tripodi F, Nicastro R, Reghellin V, Coccetti P | title = Post-translational modifications on yeast carbon metabolism: Regulatory mechanisms beyond transcriptional control | journal = Biochimica et Biophysica Acta (BBA) - General Subjects | volume = 1850 | issue = 4 | pages = 620–627 | date = April 2015 | pmid = 25512067 | doi = 10.1016/j.bbagen.2014.12.010 | hdl = 10281/138736 | hdl-access = free }}</ref>

== ATP is produced by phosphorylation== Although most often discussed in terms of the ''consumption'' of ATP (GTP and others), phosphorylation must also be involved in the production of these energy-rich species. ATP is produced by:

*oxidative phosphorylation during aerobic respiration in the mitochondrion from adenosine diphosphate (ADP). *substrate-level phosphorylation during glycolysis and the Krebs cycle. *By photophosphorylation in the chloroplasts of plant cells.

== Phosphorylation of glucose ==

=== Glucose metabolism === Phosphorylation of sugars is often the first stage in their catabolism. Phosphorylation allows cells to accumulate sugars because the phosphate group prevents the molecules from diffusing back across their transporter. Phosphorylation of glucose is a key reaction in sugar metabolism. The chemical equation for the conversion of D-glucose to D-glucose-6-phosphate in the first step of glycolysis is given by:

:D-glucose + ATP → D-glucose 6-phosphate + ADP

:ΔG° = −16.7 kJ/mol (° indicates measurement at standard condition)

thumb|'''Glycolysis''' is a process that breaks down glucose into 2 pyruvate molecules, using ATP and NADH as well as producing it. Glucose is converted to glucose-6-phosphate catalyzed by the enzyme hexokinase. Fructose-6-phosphate is converted to fructose 1,6-bisphosphate. This reaction is catalyzed by phosphofructokinase.

Glyceraldehyde 3-phosphate is again phosphorylated to give 1,3-bisphosphoglycerate. This reaction is catalyzed by glyceraldehyde-3-phosphate dehydrogenase (GAPDH).

=== Glycogen synthesis === The phosphorylation of glucose to glucose 6-phosphate has role in regulating glycogen synthase.

Glucose is phosphorylated to glucose 6-phosphate to allow its transport across the membrane by ATP-D-glucose 6-phosphotransferase and non-specific hexokinase (ATP-D-hexose 6-phosphotransferase).<ref name="ReferenceA" /><ref name="fasebj.org">{{cite journal | vauthors = Villar-Palasí C, Guinovart JJ | title = The role of glucose 6-phosphate in the control of glycogen synthase | journal = FASEB Journal | volume = 11 | issue = 7 | pages = 544–558 | date = June 1997 | pmid = 9212078 | doi = 10.1096/fasebj.11.7.9212078 | doi-access = free | s2cid = 2789124 }}</ref> Liver cells are freely permeable to glucose, and the initial rate of phosphorylation of glucose is the rate-limiting step in glucose metabolism by the liver.<ref name="ReferenceA">{{cite journal | vauthors = Walker DG, Rao S | title = The role of glucokinase in the phosphorylation of glucose by rat liver | journal = The Biochemical Journal | volume = 90 | issue = 2 | pages = 360–368 | date = February 1964 | pmid = 5834248 | pmc = 1202625 | doi = 10.1042/bj0900360 }}</ref>

The liver's crucial role in controlling blood sugar concentrations by breaking down glucose into carbon dioxide and glycogen is characterized by the negative Gibbs free energy (ΔG) value, which indicates that this is a point of regulation with<!-- Confusing sentence, needs rewrite -->.{{clarify|date=January 2023}} The hexokinase enzyme has a low Michaelis constant (K{{sub|m}}), indicating a high affinity for glucose, so this initial phosphorylation can proceed even when glucose levels at nanoscopic scale within the blood.

The phosphorylation of glucose can be enhanced by the binding of fructose 6-phosphate (F6P), and lessened by the binding fructose 1-phosphate (F1P). Fructose consumed in the diet is converted to F1P in the liver. This negates the action of F6P on glucokinase,<ref name="ReferenceA"/> which ultimately favors the forward reaction. The capacity of liver cells to phosphorylate fructose exceeds capacity to metabolize fructose-1-phosphate. Consuming excess fructose ultimately results in an imbalance in liver metabolism, which indirectly exhausts the liver cell's supply of ATP.<ref>{{cite web|url=http://cmgm.stanford.edu/biochem200/regulation/|title=Regulation of Glycolysis|website=cmgm.stanford.edu|access-date=2017-11-18|archive-date=2009-03-03|archive-url=https://web.archive.org/web/20090303224811/http://cmgm.stanford.edu/biochem200/regulation/}}</ref>

Allosteric activation by glucose-6-phosphate, which acts as an effector, stimulates glycogen synthase, and glucose-6-phosphate may inhibit the phosphorylation of glycogen synthase by cyclic AMP-stimulated protein kinase.<ref name="fasebj.org"/>

=== Other processes === Phosphorylation of glucose is imperative in processes within the body. For example, phosphorylating glucose is necessary for insulin-dependent mechanistic target of rapamycin pathway activity within the heart. This further suggests a link between intermediary metabolism and cardiac growth.<ref>{{cite journal | vauthors = Sharma S, Guthrie PH, Chan SS, Haq S, Taegtmeyer H | title = Glucose phosphorylation is required for insulin-dependent mTOR signalling in the heart | journal = Cardiovascular Research | volume = 76 | issue = 1 | pages = 71–80 | date = October 2007 | pmid = 17553476 | pmc = 2257479 | doi = 10.1016/j.cardiores.2007.05.004 }}</ref>

==Protein phosphorylation== {{Main|Protein phosphorylation}}

Protein phosphorylation is the most common post-translational modification in eukaryotes. The most common phospho-amino acid residues are those serine, threonine, and tyrosine at a ratio of 1800:200:1.<ref name=":0">{{Cite journal |last1=Mann |first1=Matthias |last2=Ong |first2=Shao En |last3=Grønborg |first3=Mads |last4=Steen |first4=Hanno |last5=Jensen |first5=Ole N. |last6=Pandey |first6=Akhilesh |date=June 2002 |title=Analysis of protein phosphorylation using mass spectrometry: deciphering the phosphoproteome |journal=Trends in Biotechnology |volume=20 |issue=6 |pages=261–268 |doi=10.1016/s0167-7799(02)01944-3 |issn=0167-7799 |pmid=12007495}}</ref> Phosphorylation of the side chains of these residues through phosphoester bond formation, on histidine, lysine and arginine through phosphoramidate bonds, and on aspartic acid and glutamic acid through mixed anhydride linkages.

Protein phosphorylation is common on human non-canonical amino acids, including motifs containing phosphorylated histidine, aspartate, glutamate, cysteine, arginine and lysine in HeLa cell extracts.<ref name="ReferenceC">{{cite journal | vauthors = Hardman G, Perkins S, Brownridge PJ, Clarke CJ, Byrne DP, Campbell AE, Kalyuzhnyy A, Myall A, Eyers PA, Jones AR, Eyers CE | display-authors = 6 | title = Strong anion exchange-mediated phosphoproteomics reveals extensive human non-canonical phosphorylation | journal = The EMBO Journal | volume = 38 | issue = 21 | article-number = e100847 | date = October 2019 | pmid = 31433507 | pmc = 6826212 | doi = 10.15252/embj.2018100847 | doi-access = free }}</ref> Histidine phosphorylates at both the 1 and 3 N-atoms of the imidazole ring.<ref name="ncbi.nlm.nih.gov">{{cite journal | vauthors = Fuhs SR, Hunter T | title = pHisphorylation: the emergence of histidine phosphorylation as a reversible regulatory modification | journal = Current Opinion in Cell Biology | volume = 45 | pages = 8–16 | date = April 2017 | pmid = 28129587 | pmc = 5482761 | doi = 10.1016/j.ceb.2016.12.010 }}</ref><ref name="https">{{cite journal | vauthors = Fuhs SR, Meisenhelder J, Aslanian A, Ma L, Zagorska A, Stankova M, Binnie A, Al-Obeidi F, Mauger J, Lemke G, Yates JR, Hunter T | display-authors = 6 | title = Monoclonal 1- and 3-Phosphohistidine Antibodies: New Tools to Study Histidine Phosphorylation | journal = Cell | volume = 162 | issue = 1 | pages = 198–210 | date = July 2015 | pmid = 26140597 | pmc = 4491144 | doi = 10.1016/j.cell.2015.05.046 }}</ref> Phospho-tyrosine is much more stable than phospho-serine and -threonine which are in turn more stable than other phospho-amino acids,<ref name=":0" /> hence the analysis of phosphorylated histidine (and other non-canonical amino acids) using standard biochemical and mass spectrometric approaches is much more challenging<ref name="ReferenceC" /><ref>{{cite journal | vauthors = Gonzalez-Sanchez MB, Lanucara F, Hardman GE, Eyers CE | title = Gas-phase intermolecular phosphate transfer within a phosphohistidine phosphopeptide dimer | journal = International Journal of Mass Spectrometry | volume = 367 | pages = 28–34 | date = June 2014 | pmid = 25844054 | pmc = 4375673 | doi = 10.1016/j.ijms.2014.04.015 | bibcode = 2014IJMSp.367...28G }}</ref><ref name="ReferenceB">{{cite journal | vauthors = Gonzalez-Sanchez MB, Lanucara F, Helm M, Eyers CE | title = Attempting to rewrite History: challenges with the analysis of histidine-phosphorylated peptides | journal = Biochemical Society Transactions | volume = 41 | issue = 4 | pages = 1089–1095 | date = August 2013 | pmid = 23863184 | doi = 10.1042/bst20130072 }}</ref> and special procedures and separation techniques are required for their preservation alongside classical Ser, Thr and Tyr phosphorylation.<ref>{{cite bioRxiv|vauthors=Hardman G, Perkins S, Ruan Z, Kannan N, Brownridge P, Byrne DP, Eyers PA, Jones AR, Eyers CE |title=Extensive non-canonical phosphorylation in human cells revealed using strong-anion exchange-mediated phosphoproteomics|year=2017|biorxiv=10.1101/202820}}</ref>

The prominent role of protein phosphorylation in biochemistry is illustrated by the many publication on the subject (as of March 2015, the MEDLINE database returns over 240,000 articles, mostly on ''protein'' phosphorylation).

==Further reading== <ref>{{cite journal |doi=10.1021/cr000225s |title=Structural Basis for Control by Phosphorylation |date=2001 |last1=Johnson |first1=Louise N. |last2=Lewis |first2=Richard J. |journal=Chemical Reviews |volume=101 |issue=8 |pages=2209–2242 |pmid=11749371 }}</ref> <ref>{{cite journal |doi=10.1021/cr000243+ |title=Histidine Phosphorylation and Two-Component Signaling in Eukaryotic Cells |date=2001 |last1=Saito |first1=Haruo |journal=Chemical Reviews |volume=101 |issue=8 |pages=2497–2510 |pmid=11749385 }}</ref> <ref>{{cite journal |doi=10.1021/cr010144b |title=Introduction: Protein Phosphorylation and Signaling |date=2001 |last1=Ahn |first1=Natalie |journal=Chemical Reviews |volume=101 |issue=8 |pages=2207–2208 |doi-access=free }}</ref> <ref>{{cite journal |doi=10.1021/acs.chemrev.8b00442 |title=Site-Selective Functionalization of Hydroxyl Groups in Carbohydrate Derivatives |date=2018 |last1=Dimakos |first1=Victoria |last2=Taylor |first2=Mark S. |journal=Chemical Reviews |volume=118 |issue=23 |pages=11457–11517 |pmid=30507165 }}</ref>

== See also == * Moiety conservation * Phosida * Phosphoamino acid analysis * Phospho3D {{Clear}}

== References == {{Reflist|colwidth=28em}}

== External links == *[https://web.archive.org/web/20090416125554/http://natureprotocols.com/2007/01/10/functional_analyses_for_sitesp.php Functional analyses for site-specific phosphorylation of a target protein in cells (A Protocol)]

{{Protein posttranslational modification}} {{Authority control}}

Category:Cell biology Category:Cell signaling Category:Phosphorus Category:Post-translational modification