ISSN:
1432-072X
Keywords:
Divalent cation
;
Manganese
;
Nitrogenase activity
;
Glutamine synthetase
;
Enzyme regulation
;
Azotobacter chroococcum
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Incubation of Azotobacter chroococcum in the presence of micromolar concentrations of MnCl2, but not MgCl2, prevented nitrogenase activity from NH 4 + inhibition. Mg(II), at a 100-fold concentration with respect to Mn(II), counteracted the protective effect of Mn(II) on nitrogenase activity. When Mn(II) was added to cells that had been given NH4Cl, stopping of NH 4 + uptake and recovery of nitrogenase activity took place, and a raise of NH 4 + concentration in medium developed. Furthermore, incubation of A. chroococcum cells with 20 μM Mn(II) under air, but not under an argon: oxygen (79%:21%) gas mixture, resulted in NH 4 + excretion to the external medium. The Mn(II)-mediated uncoupling of nitrogen fixation from ammonium assimilation leads us to conclude that Mn(II) may act as a physiological inhibitor of glutamine synthetase.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00276524
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