phytochelatin
{{Short description|Poly-glutathione peptides composed of (Glu-Cys)n-Gly where n is two to seven}}
Phytochelatins are oligomers of glutathione, produced by the enzyme phytochelatin synthase. They are found in plants, fungi, nematodes and all groups of algae including cyanobacteria. Phytochelatins act as chelators, and are important for heavy metal detoxification.{{cite journal |author1=Suk-Bong Ha |author2=Aaron P. Smith |author3=Ross Howden |author4=Wendy M. Dietrich |author5=Sarah Bugg |author6=Matthew J. O'Connell |author7=Peter B. Goldsbrough |author8=Christopher S. Cobbett |name-list-style=amp | url = http://www.plantcell.org/cgi/content/full/11/6/1153 | title = Phytochelatin Synthase Genes from Arabidopsis and the Yeast Schizosaccharomyces pombe | journal = Plant Cell | volume = 11 | pages = 1153–1164 | year = 1999 | doi = 10.1105/tpc.11.6.1153 | pmid = 10368185 | issue = 6 | pmc = 144235 | access-date = 2014-01-13}}{{cite journal |author1=Olena K. Vatamaniuk |author2=Elizabeth A. Bucher |author3=James T. Ward |author4=Philip A. Rea | title = A new pathway for heavy metal detoxification in animals: phytochelatin synthase is required for cadmium tolerance in Caenorhabditis elegans | journal = J. Biol. Chem. | year = 2001 | pmid = 11313333 | doi = 10.1074/jbc.C100152200 | volume = 276 | pages = 20817–20 | issue = 24| doi-access = free }}[http://www.embl-ebi.ac.uk/interpro/DisplayIproEntry?ac=IPR007719 InterPro database page on phytochelatin synthase]{{Dead link|date=May 2020 |bot=InternetArchiveBot |fix-attempted=yes }} They are abbreviated PC2 through PC11.
A mutant Arabidopsis thaliana lacking phytochelatin synthase is very sensitive to cadmium, but it grows just as well as the wild-type plant at normal concentrations of zinc and copper, two essential metal ions, indicating that phytochelatin is only involved in resistance to metal poisoning.{{cite book|last1=Buchanan |last2=Gruissem |last3=Jones |title=Biochemistry & molecular biology of plants |edition=1st |publisher=American Society of Plant Physiology |year=2000}}
Because phytochelatin synthase uses glutathione with a blocked thiol group in the synthesis of phytochelatin, the presence of heavy metal ions that bind to glutathione causes the enzyme to work faster. Therefore, the amount of phytochelatin increases when the cell needs more phytochelatin to survive in an environment with high concentrations of metal ions.{{cite journal |author1=O. K. Vatamaniuk |author2=S. Mari |author3=Y. Lu |author4=P. A. Rea |name-list-style=amp | title = Mechanism of Heavy Metal Ion Activation of Phytochelatin (PC) Synthase | journal = J. Biol. Chem. | volume = 275 | issue = 40 | pages = 31451–31459 | year = 2000 | doi = 10.1074/jbc.M002997200 | pmid = 10807919| doi-access = free }}
Phytochelatin binds to Pb ions leading to sequestration of Pb ions in plants and thus serves as an important component of the detoxification mechanism in plants.{{cite journal |author1= Dharmendra K. Gupta |author2= Huanggang Huang |author3= Francisco J Corpas |title= Lead tolerance in plants: Strategies for Phytoremediation |journal= Environmental Science and Pollution Research International | volume = 20 | pages = 1-2 | year = 2013 | pmid = 23338995 | doi = 10.1007/s11356-013-1485-4}} Phytochelatin seems to be transported into the vacuole of plants, so that the metal ions it carries are stored safely away from the proteins of the cytosol.
Related peptides
There are groups of other peptides with a similar structure to phytochelatin, but where the last amino acid is not glycine:{{cite journal | author = Masahiro Inouhe | doi =10.1590/S1677-04202005000100006 | title = Phytochelatins | year = 2005 | journal = Brazilian Journal of Plant Physiology | volume = 17 | pages =65–78 | doi-access = free }}
| class="wikitable"
|+Phytochelatin-like peptides | |||
| Type | Structure | Has been found in | Precursor |
|---|---|---|---|
| Phytochelatin | (γGlu-Cys)n-Gly | many organisms | Glutathione |
| Homophytochelatin | (γGlu-Cys)n-Ala | legumes | Homoglutathione |
| Desglycine phytochelatin | (γGlu-Cys)n | maize, yeasts | |
| Hydroxymethyl-phytochelatin | (γGlu-Cys)n-Ser | grasses | Hydroxymethylglutathione |
| iso-Phytochelatin (Glu) | (γGlu-Cys)n-Glu | maize | Glutamylcysteinylglutamate |
| iso-Phytochelatin (Gln) | (γGlu-Cys)n-Gln | horseradish |
History
Phytochelatin was first discovered in 1981 in fission yeast,{{cite journal | last1 = Murasugi | first1 = Akira | last2 = Wada | first2 = Chiaki | last3 = Hayashi | first3 = Yukimasa | year = 1981 | title = Cadmium-Binding Peptide Induced in Fission Yeast, Schizosaccharomyces pombe | journal = J. Biochem. | volume = 90 | issue = 5| pages = 1561–1564 | pmid = 7338524 | doi = 10.1093/oxfordjournals.jbchem.a133627 }}{{cite journal | last1 = Murasugi | first1 = Akira | last2 = Wada | first2 = Chiaki | last3 = Hayashi | first3 = Yukimasa | year = 1981 | title = Purification and Unique Properties in UV and CD Spectra of Cd-Binding Peptide 1 from Schizosaccharomyces pombe". | journal = Biochem. Biophys. Res. Commun. | volume = 103 | issue = 3| pages = 1021–1028 | doi = 10.1016/0006-291X(81)90911-6 | pmid = 7332570 }} and was named cadystin.{{cite journal | last1 = Kondo | first1 = Naoto | last2 = Imai | first2 = Kunio | last3 = Isobe | first3 = Minoru | last4 = Goto | first4 = Toshio | last5 = Murasugi | first5 = Akira | last6 = Wada-Nakagawa | first6 = Chiaki | last7 = Hayashi | first7 = Yukimasa | year = 1984 | title = Cadystin A and B, Major Unit Peptides Comprising Cadmium Binding Peptides Induced in a Fission Yeast----Separation, Revision of Structures and Synthesis | journal = Tetrahedron Lett. | volume = 25 | issue = 35| pages = 3869–3872 | doi = 10.1016/S0040-4039(01)91190-6 }} It was then found in higher plants in 1985 and was named phytochelatin. In 1989 the biosynthetic enzyme, phytochelatin synthase, was discovered.
See also
- {{cite book|last1=Farkas|first1= Etelka|last2=Buglyó|first2=Péter|chapter= Chapter 8. Lead(II) Complexes of Amino Acids, Peptides, and Other Related Ligands of Biological Interest|pages= 201–240
|publisher= de Gruyter|date= 2017|series= Metal Ions in Life Sciences|volume=17|title=Lead: Its Effects on Environment and Health|editor1-last=Astrid|editor1-first= S.|editor2-last=Helmut|editor2-first=S.|editor3-last=Sigel |editor3-first= R. K. O.|doi=10.1515/9783110434330-008|pmid= 28731301}} pp. 228–230
References
External links
- [http://www.jstage.jst.go.jp/article/jbb/92/1/92_24/_article/-char/en Strong induction of phytochelatin synthesis by zinc in marine green alga, Dunaliella tertiolecta]{{Dead link|date=May 2020 |bot=InternetArchiveBot |fix-attempted=yes }}.