Abstract: Heavy metal binding complexes found in the cytoplasm of plant cells are widely reported to be responsible fox metal resistance. It is believed that these metal binding complexes may play an important role in the accumulation of heavy metal and preventing them from entering the ptant metabolic pathways. This review summarizes information on purification, characterization and properties of these molecules. In view of their inducibility, low molecular weight, specific optical characteristics (high absorption at 254nm and low absorption at 280 nm), high cysteine content and high capacity for binding heavy metal, these complexes were once proposed to be metallothionein-like molecules. However differing from metallothionein of animal system, heavy metal binding complexes in plants are comprised mainly of three amino acids with a unique structure of (γ-Glu-Cys)n-Gly ((γ-EC)nG) (n=2—11). With the presence of γ-carboxyl group peptide linkage, the complexes are thought not to be synthesized via mRNA but the product of biosynthetic pathway using glutatkione as precursor.

Key words: Phytochelatins, Heavy metal binding peptides, Heavy metal tolerance