Mechanism of Phytochelatin Biosynthesis

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Plants and fungi synthesize short peptides termed phytochelatins when exposed to heavy metals such as cadmium. Phytochelatins are derived from a tripeptide, glutathione, by the transfer of peptide units from one glutathione molecule to another. The gene encoding for the enzyme that synthesizes phytochelatins, named phytochelatin synthase, has recently been cloned. The main objectives of the research program are three-fold: (i) To define the basic enzymology of phytochelatin synthase. (ii) Elucidation of the catalytic defect in mutants expressing variant forms of phytochelatin synthase. (iii) Crystallization and three-dimensional structure determination of phytochelatin synthase. These studies will yield fresh insights into transpeptidation reactions, in general, and the mechanism of phytochelatin synthesis, in particular. The genes encoding phytochelatin synthase could also be used to engineer plants for the remediation of heavy metal pollution.