Applied Microbiology and Biotechnology

, Volume 57, Issue 3, pp 368–373

Activation of plasma membrane H+-ATPase by ammonium ions in Aspergillus niger

  •  K. Jernejc
  •  M. Legiša
Original Paper

DOI: 10.1007/s002530100697

Cite this article as:
Jernejc, K. & Legiša, M. Appl Microbiol Biotechnol (2001) 57: 368. doi:10.1007/s002530100697

Abstract.

The addition of ammonium ions to Aspergillus niger cells originally growing on another nitrogen source resulted in rapid medium acidification. The addition of glucose or other fermentable sugars to the mycelium growing on glycerol did not have the same effect. The enzyme responsible for acidification seems to be plasma membrane H+-ATPase, which is most probably triggered by phosphorylation. Using specific activators and inhibitors, we tried to figure out which signalling pathway is involved in the process. No activation of H+-ATPase could be detected in the presence of diacylglycerol and other activators of protein kinase C, indicating that the stimulus is transmitted by another signalling chain. In the presence of inhibitors known to suppress the phosphatidyl–inositol signalling pathway, such as neomycin, compound 48/80 and calmidazolium, no increased H+-ATPase activity could be detected after the addition of ammonium ions. However, some tested inhibitors of the cAMP signalling pathway could not prevent activation of the enzyme by the stimulant. These results support the model in which ammonium-induced activation of proton extrusion in A. niger is mediated via the phosphatidyl–inositol signalling pathway, involving Ca2+/calmoduline-dependent protein kinase but not protein kinase C.

Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  •  K. Jernejc
    • 1
  •  M. Legiša
    • 1
  1. 1.National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia