Assimilatory nitrate reductase from the haloarchaeon Haloferax mediterranei: purification and characterisation

Abstract Haloferax mediterranei can use nitrate as sole nitrogen source during aerobic growth. We report here the purification and biochemical characterisation of the assimilatory nitrate reductase (EC 1.6.6.2) from H. mediterranei. The enzyme, as isolated, was composed of two subunits (105±1.3 kDa...

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Bibliographic Details
Published in:FEMS microbiology letters 2001-11, Vol.204 (2), p.381-385
Main Authors: Martı́nez-Espinosa, Rosa M, Marhuenda-Egea, Frutos C, Bonete, Marı́a José
Format: Article
Language:English
Subjects:
Archaeon
Assimilatory nitrate pathway
Dimers
Enzymes
Ferredoxin
Gel filtration
Halophile
High temperature
Methyl viologen
Microbiology
NADH
NADP
Nicotinamide adenine dinucleotide
Nitrate reductase
Nitrates
Photosynthesis
Purification
Reductases
Sodium chloride
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Summary:Abstract Haloferax mediterranei can use nitrate as sole nitrogen source during aerobic growth. We report here the purification and biochemical characterisation of the assimilatory nitrate reductase (EC 1.6.6.2) from H. mediterranei. The enzyme, as isolated, was composed of two subunits (105±1.3 kDa and 50±1.3 kDa) and behaved as a dimer during gel filtration (132±6 kDa). A pH of 9 and elevated temperatures up to 80°C (at 3.1 M NaCl) are necessary for optimum activity. The enzyme stability and activity of the enzyme depend upon the salt concentration. Reduced methyl viologen was as effective as the natural electron donor ferredoxin in the catalytic process. In contrast, NADPH and NADH, which are electron donors in nitrate reductases from different non-photosynthetic bacteria, were ineffective.
ISSN:0378-1097
1574-6968
DOI:10.1111/j.1574-6968.2001.tb10914.x