Phytochelatin synthase is the enzyme responsible for the synthesis of heavy-metal-binding peptides (phytochelatins) from glutathione and related thiols [2]. The crystal structure of a member of this family shows it to possess a papain fold [3]. The enzyme catalyses the deglycination of a GSH donor molecule [3]. The enzyme contains a catalytic triad of cysteine, histidine and aspartate residues.

1: Tolerance to toxic metals by a gene family of phytochelatin synthases from plants and yeast. Clemens S, Kim EJ, Neumann D, Schroeder JI; EMBO J 1999;18:3325-3333. PMID:10369673

2: Worms take the 'phyto' out of 'phytochelatins'. Vatamaniuk OK, Bucher EA, Ward JT, Rea PA; Trends Biotechnol 2002;20:61-64. PMID:11814595

3: A papain-like enzyme at work: native and acyl-enzyme intermediate structures in phytochelatin synthesis. Vivares D, Arnoux P, Pignol D; Proc Natl Acad Sci U S A. 2005;102:18848-18853. PMID:16339904