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Applied and Environmental Microbiology, November 2001, p. 5122-5126, Vol. 67, No. 11
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.11.5122-5126.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Characterization of the Reduction of Selenate and Tellurite by Nitrate Reductases

Monique Sabaty,1,* Cécile Avazeri,1 David Pignol,1,2 and André Vermeglio1

CEA/Cadarache, DSV, DEVM, Laboratoire de Bioénergétique Cellulaire, 13108 St. Paul lez Durance Cedex,1 and Laboratoire de Cristallographie et Cristallogénèse des Protéines, Institut de Biologie Structurale JP Ebel CEA-CNRS, 38027 Grenoble Cedex 1,2 France

Received 29 March 2001/Accepted 9 August 2001

Preliminary studies showed that the periplasmic nitrate reductase (Nap) of Rhodobacter sphaeroides and the membrane-bound nitrate reductases of Escherichia coli are able to reduce selenate and tellurite in vitro with benzyl viologen as an electron donor. In the present study, we found that this is a general feature of denitrifiers. Both the periplasmic and membrane-bound nitrate reductases of Ralstonia eutropha, Paracoccus denitrificans, and Paracoccus pantotrophus can utilize potassium selenate and potassium tellurite as electron acceptors. In order to characterize these reactions, the periplasmic nitrate reductase of R. sphaeroides f. sp. denitrificans IL106 was histidine tagged and purified. The Vmax and Km were determined for nitrate, tellurite, and selenate. For nitrate, values of 39 µmol · min-1 · mg-1 and 0.12 mM were obtained for Vmax and Km, respectively, whereas the Vmax values for tellurite and selenate were 40- and 140-fold lower, respectively. These low activities can explain the observation that depletion of the nitrate reductase in R. sphaeroides does not modify the MIC of tellurite for this organism.

* Corresponding author. Mailing address: CEA/Cadarache, DSV, DEVM, Laboratoire de Bioénergétique Cellulaire, 13108 St. Paul lez Durance Cedex, France. Phone: (33) 4 42 25 35 70. Fax: (33) 4 42 25 47 01. E-mail: address: msabaty{at}cea.fr.

Applied and Environmental Microbiology, November 2001, p. 5122-5126, Vol. 67, No. 11
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.11.5122-5126.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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Copyright © 2001 by the American Society for Microbiology. All rights reserved.