Phytochelatin

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.[1][2][3] They are abbreviated PC2 through PC11.

Chemical structure of phytochelatin. n = 2–11.

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.[4]

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.[5]

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.[6] 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.[4]

There are groups of other peptides with a similar structure to phytochelatin, but where the last amino acid is not glycine:[4][7]

Phytochelatin-like peptides
TypeStructureHas been found inPrecursor
Phytochelatin(γGlu-Cys)n-Glymany organismsGlutathione
Homophytochelatin(γGlu-Cys)n-AlalegumesHomoglutathione
Desglycine phytochelatin(γGlu-Cys)nmaize, yeasts
Hydroxymethyl-phytochelatin(γGlu-Cys)n-SergrassesHydroxymethylglutathione
iso-Phytochelatin (Glu)(γGlu-Cys)n-GlumaizeGlutamylcysteinylglutamate
iso-Phytochelatin (Gln)(γGlu-Cys)n-Glnhorseradish

History

Phytochelatin was first discovered in 1981 in fission yeast,[8][9] and was named cadystin.[10] It was then found in higher plants in 1985 and was named phytochelatin. In 1989 the biosynthetic enzyme, phytochelatin synthase, was discovered.[7]

See also
  • Farkas, Etelka; Buglyó, Péter (2017). "Chapter 8. Lead(II) Complexes of Amino Acids, Peptides, and Other Related Ligands of Biological Interest". In Astrid, S.; Helmut, S.; Sigel, R. K. O. (eds.). Lead: Its Effects on Environment and Health. Metal Ions in Life Sciences. Vol. 17. de Gruyter. pp. 201–240. doi:10.1515/9783110434330-008. PMID 28731301. pp. 228–230
  • Dunaliella

References
  1. Suk-Bong Ha; Aaron P. Smith; Ross Howden; Wendy M. Dietrich; Sarah Bugg; Matthew J. O'Connell; Peter B. Goldsbrough & Christopher S. Cobbett (1999). "Phytochelatin Synthase Genes from Arabidopsis and the Yeast Schizosaccharomyces pombe". Plant Cell. 11 (6): 1153–1164. doi:10.1105/tpc.11.6.1153. PMC 144235. PMID 10368185. Retrieved 2014-01-13.
  2. Olena K. Vatamaniuk; Elizabeth A. Bucher; James T. Ward; Philip A. Rea (2001). "A new pathway for heavy metal detoxification in animals: phytochelatin synthase is required for cadmium tolerance in Caenorhabditis elegans". J. Biol. Chem. 276 (24): 20817–20. doi:10.1074/jbc.C100152200. PMID 11313333.
  3. InterPro database page on phytochelatin synthase
  4. Buchanan; Gruissem; Jones (2000). Biochemistry & molecular biology of plants (1st ed.). American Society of Plant Physiology.
  5. O. K. Vatamaniuk; S. Mari; Y. Lu & P. A. Rea (2000). "Mechanism of Heavy Metal Ion Activation of Phytochelatin (PC) Synthase". J. Biol. Chem. 275 (40): 31451–31459. doi:10.1074/jbc.M002997200. PMID 10807919.
  6. Dharmendra K. Gupta; Huanggang Huang; Francisco J Corpas (2013). "Lead tolerance in plants: Strategies for Phytoremediation". Environmental Science and Pollution Research International. 20: 1–2. doi:10.1007/s11356-013-1485-4. PMID 23338995.
  7. Masahiro Inouhe (2005). "Phytochelatins". Brazilian Journal of Plant Physiology. 17: 65–78. doi:10.1590/S1677-04202005000100006.
  8. Murasugi, Akira; Wada, Chiaki; Hayashi, Yukimasa (1981). "Cadmium-Binding Peptide Induced in Fission Yeast, Schizosaccharomyces pombe". J. Biochem. 90 (5): 1561–1564. doi:10.1093/oxfordjournals.jbchem.a133627. PMID 7338524.
  9. Murasugi, Akira; Wada, Chiaki; Hayashi, Yukimasa (1981). "Purification and Unique Properties in UV and CD Spectra of Cd-Binding Peptide 1 from Schizosaccharomyces pombe"". Biochem. Biophys. Res. Commun. 103 (3): 1021–1028. doi:10.1016/0006-291X(81)90911-6. PMID 7332570.
  10. Kondo, Naoto; Imai, Kunio; Isobe, Minoru; Goto, Toshio; Murasugi, Akira; Wada-Nakagawa, Chiaki; Hayashi, Yukimasa (1984). "Cadystin A and B, Major Unit Peptides Comprising Cadmium Binding Peptides Induced in a Fission Yeast----Separation, Revision of Structures and Synthesis". Tetrahedron Lett. 25 (35): 3869–3872. doi:10.1016/S0040-4039(01)91190-6.
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