Omanische Heilpflanze im Fokus der Phytochemie IPB-Wissenschaftler und Partner aus Dhofar haben jüngst die omanische Heilpflanze Terminalia dhofarica unter die phytochemische Lupe genommen. Die Pflanze ist reich an…
Geschmack ist vorhersagbar: Mit FlavorMiner. FlavorMiner heißt das Tool, das IPB-Chemiker und Partner aus Kolumbien jüngst entwickelt haben. Das Programm kann, basierend auf maschinellem Lernen (KI), anhand der…
Harada, E.; von Roepenack-Lahaye, E.; Clemens, S.;A cyanobacterial protein with similarity to phytochelatin synthases catalyzes the conversion of glutathione to γ-glutamylcysteine and lacks phytochelatin synthase activityPhytochemistry653179-3185(2004)DOI: 10.1016/j.phytochem.2004.09.017
Phytochelatins are glutathione-derived, non-translationally synthesized peptides essential for cadmium and arsenic detoxification in plant, fungal and nematode model systems. Recent sequencing programs have revealed the existence of phytochelatin synthase-related genes in a wide range of organisms that have not been reported yet to produce phytochelatins. Among those are several cyanobacteria. We have studied one of the encoded proteins (alr0975 from Nostoc sp. strain PCC 7120) and demonstrate here that it does not possess phytochelatin synthase activity. Instead, this protein catalyzes the conversion of glutathione to γ-glutamylcysteine. The thiol spectrum of yeast cells expressing alr0975 shows the disappearance of glutathione and the formation of a compound that by LC–MSMS analysis was unequivocally identified as γ-glutamylcysteine. Purified recombinant protein catalyzes the respective reaction. Unlike phytochelatin synthesis, the conversion of glutathione to γ-glutamylcysteine is not dependent on activation by metal cations. No evidence was found for the accumulation of phytochelatins in cyanobacteria even after prolonged exposure to toxic Cd2+ concentrations. Expression of alr0975 was detected in Nostoc sp. cells with an antiserum raised against the protein. No indication for a responsiveness of expression to toxic metal exposure was found. Taken together, these data provide further evidence for possible additional functions of phytochelatin synthase-related proteins in glutathione metabolism and provide a lead as to the evolutionary history of phytochelatin synthesis.
Publikation
Clemens, S.; Palmgren, M. G.; Krämer, U.;A long way ahead: understanding and engineering plant metal accumulationTrends Plant Sci.7309-315(2002)DOI: 10.1016/S1360-1385(02)02295-1
Some plants can hyperaccumulate metal ions that are toxic to virtually all other organisms at low dosages. This trait could be used to clean up metal-contaminated soils. Moreover, the accumulation of heavy metals by plants determines both the micronutrient content and the toxic metal content of our food. Complex interactions of transport and chelating activities control the rates of metal uptake and storage. In recent years, several key steps have been identified at the molecular level, enabling us to initiate transgenic approaches to engineer the transition metal content of plants.