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- Title
Ammonium-assimilating enzymes and their regulation in wild and NADP-glutamate dehydrogenase-deficient strains of the ectomycorrhizal fungus Hebeloma cylindrosporum.
- Authors
Chalote, Michel; Brun, Annick; Debaud, Jean Claude; Botton, Bernard
- Abstract
Hebeloma cylindrosporum strain h 17 was grown on media containing either glutamate or ammonium as nitrogen source. Growth tests and in vitro activity measure- ments revealed that both glutamine synthetase (GS. EC 6.3.1.2) and NADP-specific glutamate dehydrogenase (NADP-GDH, EC 1.4.1.4) are fully functional in wild type mycelia grown on glutamate or ammonium as sole nitrogen source, However, NADP-GDH appeared to be more active than GS in stationary growing mycelia. NADP-GDH is also able to sustain adequate ammonium assimilation in methionine sulfoximine (MSX)-treated mycelia since they grew as well as mycelia fed with ammonium alone. The NADP-GDH also appeared to be L-glutamate inducible whereas GS was repressed by ammononium. The NADP-GDH deficient strain, when transferred from a glutamate containing medium to an ammonium containing medium, exhibited a derepressed GS, although this enzyme did not fully substitute for the deficiency of NADP-GDH in ammonium assimilation. The low NADP-GDU activity of the mutant strain exhibited a reduced mobility on a 6% constant polyacrylamide gel. By contrast, the two enzymes had identical molecular weights, estimated to be ca 295 kDa on gradient polyacrylamide gel. The involvement of NADP-GDH and GS enzymes in nitrogen assimilation is discussed.
- Subjects
ECTOMYCORRHIZAL fungi; HEBELOMA; AMINO acids; NITROGEN; GLUTAMATE decarboxylase; POLYACRYLAMIDE; PLANT enzymes
- Publication
Physiologia Plantarum, 1991, Vol 83, Issue 1, p122
- ISSN
0031-9317
- Publication type
Article
- DOI
10.1111/j.1399-3054.1991.tb01290.x