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Termination of the phytochelatin synthase reaction through sequestration of heavy metals by the reaction product
Author(s) -
Loeffler Susanne,
Hochberger Andreas,
Grill Erwin,
Winnacker Ernst-L.,
Zenk Meinhart H.
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)81611-4
Subject(s) - phytochelatin , chemistry , enzyme , chelation , glutathione , metal , glutathione synthetase , stereochemistry , biochemistry , organic chemistry
The newly discovered enzyme γ‐glutamylcysteine dipeptidyl transpeptidase was purified to apparent homogeneity from cell suspension cultures of Silene cucubalus . The enzyme catalyzes, in the presence of heavy metal ions, the formation of metal chelating peptides, the phytochelatins, from glutathione. The stoichiometry of the transfer reaction for the first phytochelatin member was determined to be: 2 (γ‐Glu‐Cys)‐Gly → (γ‐Glu‐Cys) 2 ‐Gly + Gly. The enzyme is self regulated in that the reaction products, the phytochelatins, chelate the enzyme activating metal, thus terminating the enzymatic reaction. The higher order phytochelatins have a higher relative complexing affinity than the lower ones, as judged from their ability to terminate the enzymatic reaction.