cDNA cloning and expression analysis of Eisenia fetida (Annelida: Oligochaeta) phytochelatin synthase under cadmium exposure.

Metallothioneins (MTs) are central to trace metal homeostasis and detoxification throughout biological systems. Prokaryotes, plants, and fungi utilize both gene encoded cysteine-rich polypeptides (classically designated Class I and II MTs) and enzymatically synthesized cysteine-rich peptides (classically designated Class III MTs or phytochelatins). In contrast, although gene encoded MTs are ubiquitous in animal species the identification of a functional phytochelatin synthase in the nematode Caenorhabditis elegans, a representative member of the Ecdysozoa, provided the first evidence for these metal-binding peptides in animals.