Open AccessAssimilatory nitrate reductase from the haloarchaeon Haloferax mediterranei : purification and characterisation
Author(s) -
Martı́nezEspinosa Rosa M,
MarhuendaEgea Frutos C,
Bonete Marı́a José
Publication year - 2001
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2001.tb10914.x
Subject(s) - nitrate reductase , biochemistry , nitrate , enzyme , ferredoxin , chemistry , bacteria , biology , organic chemistry , genetics
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.