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Journal of Bacteriology, February 2000, p. 796-804, Vol. 182, No. 3
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Purification and Characterization of an Iron Superoxide Dismutase and a Catalase from the Sulfate-Reducing Bacterium Desulfovibrio gigas

Wagner G. Dos Santos,1,* Isabel Pacheco,1 Ming-Yih Liu,2 Miguel Teixeira,1 António V. Xavier,1 and Jean LeGall1,2

Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2780 Oeiras, Portugal,1 and Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 306022

Received 29 July 1999/Accepted 4 November 1999

The iron-containing superoxide dismutase (FeSOD; EC 1.15.1.1) and catalase (EC 1.11.1.6) enzymes constitutively expressed by the strictly anaerobic bacterium Desulfovibrio gigas were purified and characterized. The FeSOD, isolated as a homodimer of 22-kDa subunits, has a specific activity of 1,900 U/mg and exhibits an electron paramagnetic resonance (EPR) spectrum characteristic of high-spin ferric iron in a rhombically distorted ligand field. Like other FeSODs from different organisms, D. gigas FeSOD is sensitive to H2O2 and azide but not to cyanide. The N-terminal amino acid sequence shows a high degree of homology with other SODs from different sources. On the other hand, D. gigas catalase has an estimated molecular mass of 186 ± 8 kDa, consisting of three subunits of 61 kDa, and shows no peroxidase activity. This enzyme is very sensitive to H2O2 and cyanide and only slightly sensitive to sulfide. The native enzyme contains one heme per molecule and exhibits a characteristic high-spin ferric-heme EPR spectrum (gy,x = 6.4, 5.4); it has a specific activity of 4,200 U/mg, which is unusually low for this class of enzyme. The importance of these two enzymes in the context of oxygen utilization by this anaerobic organism is discussed.

* Corresponding author. Mailing address: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande, Apartado 127, 2780 Oeiras, Portugal. Phone: (351)21-446-9825. Fax: (351)21-442-8766. E-mail: Wagner{at}itqb.unl.pt.

Journal of Bacteriology, February 2000, p. 796-804, Vol. 182, No. 3
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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