Characterization of arsenate reductase in the extract of roots and fronds of Chinese brake fern, an arsenic hyperaccumulator.
Root extracts from the arsenic (As) hyperaccumulating Chinese brake fern (Pteris vittata) were shown to be able to reduce arsenate to arsenite. An arsenate reductase (AR) in the fern showed a reaction mechanism similar to the previously reported Acr2p, an AR from yeast (Saccharomyces cerevisiae), using glutathione as the electron donor. Substrate specificity as well as sensitivity toward inhibitors for the fern AR (phosphate as a competitive inhibitor, arsenite as a noncompetitive inhibitor) was also similar to Acr2p. Kinetic analysis showed that the fern AR had a Michaelis constant value of 2.33 mM for arsenate, 15-fold lower than the purified Acr2p. The AR-specific activity of the fern roots treated with 2 mM arsenate for 9 d was at least 7 times higher than those of roots and shoots of plant species that are known not to tolerate arsenate. A T-DNA knockout mutant of Arabidopsis (Arabidopsis thaliana) with disruption in the putative Acr2 gene had no AR activity. We could not detect AR activity in shoots of the fern. These results indicate that (1) arsenite, the previously reported main storage form of As in the fern fronds, may come mainly from the reduction of arsenate in roots; and (2) AR plays an important role in the detoxification of As in the As hyperaccumulating fern.
Duan
Gui-Lan
GL
Research Center for Eco-Environmental Sciences.
Zhu
Yong-Guan
YG
Tong
Yi-Ping
YP
Cai
Chao
C
Kneer
Ralf
R
D053502:Arsenate Reductases; D001151:Arsenic / Q000493:pharmacokinetics*; D053501:Arsenite Transporting ATPases; D002681:China; D005978:Glutathione / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D016623:Ion Pumps / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology; D018517:Plant Roots / Q000201:enzymology; D032495:Pteris / Q000201:enzymology*; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins; D014162:Transfection
D016623:Ion Pumps; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C506971:ARR2 protein, S cerevisiae; D053502:Arsenate Reductases; D053501:Arsenite Transporting ATPases; D005978:Glutathione; D001151:Arsenic