A pseudo-phytochelatin synthase in the ciliated protozoan Tetrahymena thermophila.
Phytochelatins (PCs) and metallothioneins (MTs) are the two major heavy metal chelating peptides in eukaryotes. We report here on the identification of a biosynthetically inactive pseudo-phytochelatin synthase enzyme (TtpsiPCS) in the ciliate Tetrahymena thermophila, the first of this kind (pseudo-PCS) to be described in eukaryotes. TtpsiPCS which resembles a true PCS at the N-terminal region, while it is most divergent in its Cys-poor C-terminal region, was found to be up-regulated under cadmium stress conditions. However, only glutathione (GSH) hydrolysis products, but not PCs, could be detected in extracts from Cd-treated cells. The latter feature is reminiscent of pseudo-PCS enzymes recently identified in cyanobacteria, which are also biosynthetically inactive, but capable to hydrolyze GSH.
Amaro
Francisco
F
Departamento de Microbiología-III, Facultad de Biología, Universidad Complutense (UCM), 28040 Madrid, Spain.
Ruotolo
Roberta
R
Martín-González
Ana
A
Faccini
Andrea
A
Ottonello
Simone
S
Gutiérrez
Juan-Carlos
JC
D019881:Aminoacyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D019256:Cadmium Chloride / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D054811:Phytochelatins / Q000096:biosynthesis; D016808:Tetrahymena thermophila / Q000187:drug effects / Q000201:enzymology*
D054811:Phytochelatins; D019881:Aminoacyltransferases; C093784:glutathione gamma-glutamylcysteinyltransferase; D005978:Glutathione; D019256:Cadmium Chloride