View source for Biology:Shikimate pathway

{{Short description|Biosynthetic Pathway}}
The '''shikimate pathway''' ('''[[Chemistry:Shikimic acid|shikimic acid]] pathway''') is a seven-step [[Biology:Metabolic pathway|metabolic pathway]] used by [[Biology:Bacterium|bacteria]], [[Biology:Archaea|archaea]], [[Biology:Fungus|fungi]], algae, some [[Biology:Protozoa|protozoans]], and [[Biology:Plant|plant]]s for the [[Biology:Biosynthesis|biosynthesis]] of [[Chemistry:Folate|folate]]s and [[Chemistry:Aromatic amino acid|aromatic amino acid]]s ([[Chemistry:Tryptophan|tryptophan]], [[Chemistry:Phenylalanine|phenylalanine]], and [[Chemistry:Tyrosine|tyrosine]]). This pathway is not found in animal cells.

The seven enzymes involved in the shikimate pathway are [[Biology:DAHP synthase|DAHP synthase]], [[Biology:3-dehydroquinate synthase|3-dehydroquinate synthase]], [[Biology:3-dehydroquinate dehydratase|3-dehydroquinate dehydratase]], [[Biology:Shikimate dehydrogenase|shikimate dehydrogenase]], [[Biology:Shikimate kinase|shikimate kinase]], [[Biology:EPSP synthase|EPSP synthase]], and [[Biology:Chorismate synthase|chorismate synthase]]. The pathway starts with two [[Biology:Substrate (biochemistry)|substrate]]s, phosphoenol pyruvate and erythrose-4-phosphate, and ends with chorismate (chrorismic acid), a substrate for the three aromatic amino acids. The fifth [[Biology:Enzyme|enzyme]] involved is the [[Biology:Shikimate kinase|shikimate kinase]], an enzyme that catalyzes the [[Chemistry:Adenosine triphosphate|ATP]]-dependent [[Biology:Phosphorylation|phosphorylation]] of [[Chemistry:Shikimic acid|shikimate]] to form shikimate 3-phosphate (shown in the figure below).<ref>{{Cite journal 
| last1 = Herrmann | first1 = K. M. 
| last2 = Weaver | first2 = L. M. 
| doi = 10.1146/annurev.arplant.50.1.473 
| title = The Shikimate Pathway 
| journal = Annual Review of Plant Physiology and Plant Molecular Biology 
| volume = 50 
| pages = 473–503 
| year = 1999 
| pmid = 15012217 
| pmc = 
}}</ref> Shikimate 3-phosphate is then coupled with phosphoenol pyruvate to give 5-enolpyruvylshikimate-3-phosphate via the enzyme [[Biology:EPSP synthase|5-enolpyruvylshikimate-3-phosphate (EPSP) synthase]].
Glyphosate, the herbicidal ingredient in [[Biology:Roundup (herbicide)|Roundup]], is a competitive inhibitor of EPSP synthase, acting as a transition state analog that binds more tightly to the EPSPS-S3P complex than PEP and inhibits the shikimate pathway.

:[[File:Chorismate pathway 1.png|450px]]

Then 5-enolpyruvylshikimate-3-phosphate is transformed into chorismate by a [[Biology:Chorismate synthase|chorismate synthase]].
:[[File:Chorismate pathway 2.png|450px]]

[[Chemistry:Prephenic acid|Prephenic acid]] is then synthesized by a [[Chemistry:Claisen rearrangement|Claisen rearrangement]] of chorismate by [[Biology:Chorismate mutase|chorismate mutase]].<ref>{{cite journal
 | title = On the mechanism of the chorismate mutase reaction
 | author = Helmut Goerisch 
 | journal = Biochemistry
 | year = 1978
 | pages = 3700–3705
 | doi = 10.1021/bi00611a004
 | volume = 17
 | issue = 18| pmid = 100134 
 }}</ref><ref>{{cite journal 
 | title = Thermodynamics of the Conversion of Chorismate to Prephenate: Experimental Results and Theoretical Predictions  
 | author1 = Peter Kast
 | author2 = Yadu B. Tewari
 | author3 = Olaf Wiest
 | author4 = Donald Hilvert
 | author5 = Kendall N. Houk
 | author6 = Robert N. Goldberg
 | journal = J. Phys. Chem. B 
 | volume = 101 
 | issue = 50
 | pages = 10976–10982 
 | year = 1997  
 | doi = 10.1021/jp972501l}}</ref>

:[[File:Prephenate biosynthesis.png|350px]]

Prephenate is [[Chemistry:Oxidative decarboxylation|oxidatively decarboxylated]] with retention of the hydroxyl group to give ''p''-hydroxyphenylpyruvate, which is [[Chemistry:Transamination|transaminated]] using [[Chemistry:Glutamic acid|glutamate]] as the nitrogen source to give [[Chemistry:Tyrosine|tyrosine]] and [[Chemistry:Alpha-Ketoglutaric acid|α-ketoglutarate]].

:[[File:Tyrosine biosynthesis.svg|450px]]

== References ==
<references />

== Bibliography ==

* {{cite book |title=Shikimic Acid: Metabolism and Metabolites |author=Edwin Haslam |year=1993 |isbn=0471939994 |edition=1st }}
* {{cite journal|last1=Brown|first1=Stewart A.|last2=Neish|first2=A. C.|title=Shikimic Acid as a Precursor in Lignin Biosynthesis|journal=Nature|volume=175|issue=4459|year=1955|pages=688–689|issn=0028-0836|doi=10.1038/175688a0|pmid=14370198|bibcode=1955Natur.175..688B|s2cid=4273320}}
* {{cite journal|last1=Weinstein|first1=L. H.|last2=Porter|first2=C. A.|last3=Laurencot|first3=H. J.|title=Role of the Shikimic Acid Pathway in the Formation of Tryptophan in Higher Plants : Evidence for an Alternative Pathway in the Bean|journal= Nature|volume=194|issue=4824|year=1962|pages=205–206|issn=0028-0836|doi=10.1038/194205a0|bibcode=1962Natur.194..205W|s2cid=4160308}}
* {{cite journal|last1=Wilson|first1=D J|last2=Patton|first2=S|last3=Florova|first3=G|last4=Hale|first4=V|last5=Reynolds|first5=K A|title=The shikimic acid pathway and polyketide biosynthesis|journal=Journal of Industrial Microbiology and Biotechnology|volume=20|issue=5|year=1998|pages=299–303|issn=1367-5435|doi=10.1038/sj.jim.2900527|s2cid=41117722|doi-access=free}}

{{MetabolismMap}}

[[Category:Metabolic pathways]]

{{Sourceattribution|Shikimate pathway}}