Current Microbiology

, Volume 30, Issue 6, pp 367–372

Glutamine synthetase/glutamate synthase ammonium-assimilating pathway in Schizosaccharomyces pombe

Authors

  • Angelos Perysinakis
    • Sector of Organic Chemistry and Biochemistry, Department of ChemistryUniversity of Ioannina
  • James R. Kinghorn
    • Division of Plant Ecology and Evolution, School of Biological and Medical SciencesUniversity of St. Andrews
  • Constantin Drainas
    • Sector of Organic Chemistry and Biochemistry, Department of ChemistryUniversity of Ioannina
Article

DOI: 10.1007/BF00369864

Cite this article as:
Perysinakis, A., Kinghorn, J.R. & Drainas, C. Current Microbiology (1995) 30: 367. doi:10.1007/BF00369864

Abstract

Kinetic parameters of glutamine synthetase (GS) and glutamate synthase (glutamineoxoglutarate aminotransferase) (GOGAT) activities, including initial velocity, pH, and temperature optima, as well as Km values, were estimated in Schizosaccharomyces pombe crude cell-free extracts. Five glutamine auxotrophic mutants of S. pombe were isolated following MNNG treatment. These were designated gln1-1,2,3,4,5, and their growth could be repaired only by glutamine. Mutants gln1-1,2,3,4,5 were found to lack GS activity, but retained wild-type levels of NADP-glutamate dehydrogenase (GDH), NAD-GDH, and GOGAT. One further glutamine auxotrophic mutant, gln1-6, was isolated and found to lack both GS and GOGAT but retained wild-type levels of NADP-GDH and NAD-GDH activities. Fortuitously, this isolate was found to harbor an unlinked second mutation (designated gog1-1), which resulted in complete loss of GOGAT activity but retained wild-type GS activity. The growth phenotype of mutant gog1-1 (in the absence of the gln1-6 mutation) was found to be indistinguishable from the wild type on various nitrogen sources, including ammonium as a sole nitrogen source. Double-mutant strains containing gog1-1 and gdh1-1 or gdh2-1 (mutations that result specifically in the abolition of NADP-GDH activity) result in a complete lack of growth on ammonium as sole nitrogen source in contrast to gdh or gog mutants alone.

Copyright information

© Springer-Verlag New York Inc 1995