title: Characterization of arsenate reductase in the extract of roots and fronds of Chinese brake fern, an arsenic hyperaccumulator.
abstract: 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.
authors.affiliation: Research Center for Eco-Environmental Sciences.
authors.forename: Gui-Lan
authors.initials: GL
authors.lastname: Duan
authors.forename: Yong-Guan
authors.initials: YG
authors.lastname: Zhu
authors.forename: Yi-Ping
authors.initials: YP
authors.lastname: Tong
authors.forename: Chao
authors.initials: C
authors.lastname: Cai
authors.forename: Ralf
authors.initials: R
authors.lastname: Kneer
mesh_terms: 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
chemical_list: 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