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.
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.
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.
Phytochelatin was first discovered in 1981 in fission yeast, and was named cadystin. It was then found in higher plants in 1985 and was named phytochelatin. In 1989 its enzyme, phytochelatin synthase, was discovered.
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