Phytochelatins
Phytochelatins (also cadystin and metallothionein Class III ) are polypeptides that are enzymatically formed in response to heavy metals in plants and fungi. They bind to heavy metals (e.g. cadmium ) and thus detoxify them.
Just like glutathione , phytochelatins consist of the amino acids glutamic acid , cysteine and glycine , whereby the γ- carboxy group (not the α-carboxy group) of the glutamic acid residue is linked to the amino group of the cysteine residue, since phytochelatins are enzymatically synthesized from glutathione. The enzyme phytochelatin synthase breaks down the glycine of a glutathione molecule and attaches another glutathione molecule. The simplest phytochelatin therefore has the structure γGlu-Cys-γGlu-Cys-Gly. This can be extended by adding one or more other γGlu-Cys. Most other polypeptides, on the other hand, are encoded by a specific gene and are synthesized during translation .
Phytochelatins are formed in response to a wide range of heavy metals and other toxic metallic and semi-metallic elements and initiate a detoxification mechanism : They bind with the sulfhydryl groups of their cysteines to the metal ions and are transported with them into the vacuole. In the vacuole, the heavy metals are shielded from the metabolism in the cytosol, so that they cannot disturb the enzymatic reactions of the metabolism there. The phytochelatin-metal complexes formed can be partially purified by chromatography and then characterized.
Phytochelatins were discovered, purified and characterized for the first time in 1985 by two research groups at about the same time.
Web links
literature
- Buchanan, BB, Gruissem, W & Jones, RL (2000): Biochemistry and molecular biology of plants. At the. Soc. Plant Physiol. ISBN 978-0-470-71421-8
- A. Singh, OP Ward: Biodegradation and Bioremediation . Springer, 2004.