Archives of Microbiology

, Volume 102, Issue 1, pp 91–94 | Cite as

Molybdenum and iron as functional constituents of the enzymes of the nitrate-reducing system of Azotobacter chroococcum

  • M. G. Guerrero
  • J. M. Vega
Short Communications


The roles of molybdenum and iron in the enzymes of the assimilatory nitrate-reducing system from Azotobacter chroococcum have been investigated.
  1. 1.

    By adding 99Mo-molybdate to a cell culture of A. chroococcum with nitrate as the nitrogen source, it has been possible to inccrporate the radioactive metal into a purified preparation of the enzyme nitrare reductase.

  2. 2.

    When 185W-tungstate was supplied to a culture medium lacking added molybdate, a 185W-labelled nitrate reductase preparation with negligible activity could be obtained. This in vivo incorporation of tungsten was competitively hindered by molybdenum.

  3. 3.

    The cellular level of nitrite reductase activity gradually increased in response to the addition of increasing amounts of iron to the culture medium. Under the same conditions, the level of nitrate reductase activity was not affected.


Key words

Azotobacter Iron Molybdenum Nitrate Nitrite Tungsten 


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Copyright information

© Springer-Verlag 1975

Authors and Affiliations

  • M. G. Guerrero
    • 1
  • J. M. Vega
    • 1
  1. 1.Departamento de Bioquímica, Facultad de Ciencias y CSICUniversidad de SevillaSevilla

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