PROSITE documentation PDOC51443
Phytochelatin synthase (PCS) domain profile


Phytochelatins (PCs) are well known as the heavy metal-detoxifying peptides in higher plants, eukaryotic algae, fungi, nematode and cyanobacteria. These peptides, of the general structure (γ-Glu-Cys)n-Gly (with n=2-11), are enzymatically synthesized from the substrate glutathione (GSH). PCs are synthesized posttranslationally by the PC synthase (PCS) (EC, a γ-glutamylcysteine (γ-EC) transpeptidase. PC synthesis is proposed to have two distinct steps: (Step1) formation of γ-EC concomitant with the cleavage of Gly from GSH; and (Step 2) transfer of the γ-EC unit to an acceptor GSH molecule or an oligomeric PC peptide (PCn). Eukaryotic PCS typically has a conserved N-terminal domain and a variable C-terminal domain, both of which are cysteine-rich. The N-terminal core domain is sufficient to confer a PCS activity and therefore can be referred to the catalytic domain. Cyanobacterial PCS contains the conserved N-terminal catalytic domain but not the variable C-terminal domain found in eukaryotic PCSs. It can act as a GSH hydrolase and weakly as a peptide ligase [1,2].

The catalytic PCS domain belongs to the petidase family C83 of the papain superfamily of cysteine proteases [E1], with the structurally conserved "catalytic triad" and oxyanion hole in the active site. It has an overall "crescent" shape with α/β fold containing eight α-helices and six β-strands (see <PDB:2BTW>) [2].

The profile we developed covers the entire PCS domain.

Last update:

March 2009 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

PCS, PS51443; Phytochelatin synthase (PCS) domain profile  (MATRIX)


1AuthorsTsuji N. Nishikori S. Iwabe O. Shiraki K. Miyasaka H. Takagi M. Hirata K. Miyamoto K.
TitleCharacterization of phytochelatin synthase-like protein encoded by alr0975 from a prokaryote, Nostoc sp. PCC 7120.
SourceBiochem. Biophys. Res. Commun. 315:751-755(2004).
PubMed ID14975765

2AuthorsVivares D. Arnoux P. Pignol D.
TitleA papain-like enzyme at work: native and acyl-enzyme intermediate structures in phytochelatin synthesis.
SourceProc. Natl. Acad. Sci. U.S.A. 102:18848-18853(2005).
PubMed ID16339904


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