Involved in the synthesis of phytochelatins (PC) and homophytochelatins (hPC), the heavy-metal-binding peptides of plants. [Glu(-Cys)](n)-Gly + glutathione + H(+) = [Glu(-Cys)](n+1)-Gly + glycine Requires cadmium for activity. Expressed in roots, nodules and leaves. By cadmium. Found in nodules. Found in roots. Not functional in yeast heterologous system. Belongs to the phytochelatin synthase family.