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ENZYMES OF AMMONIUM ASSIMILATION IN THE MYCORRHIZAL FUNGUS PEZIZELLA ERICAE READ
Author(s) -
JOHN B. J. ST.,
SMITH S. E.,
NICHOLAS D. J. D.,
SMITH F. A.
Publication year - 1985
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1985.tb02804.x
Subject(s) - glutamine synthetase , glutamate dehydrogenase , ammonium , mycelium , enzyme , ammonia , nitrogen , chemistry , assimilation (phonology) , nitrogen assimilation , glutamine , nuclear chemistry , biochemistry , botany , biology , glutamate receptor , amino acid , organic chemistry , receptor , linguistics , philosophy
S ummary Growth of Pezizella ericae Read in solution culture with ammonium (NH 4 + ) as the primary nitrogen source was accompanied by decrease in pH and ammonium concentration. Both glutamate dehydrogenase (GDH) and glutamine synthetase (GS) were involved in ammonium assimilation. Activities of these enzymes changed during the time course of the experiment (28 d). Maximum GDH activity [0.35 μol NAD(P)H oxidized min −1 mg protein −1 ] occurred when external NH 4 + concentration was high (5 to 10 mM). Maximum GS activity (0.2 μol of γ‐glutamyl hydroxamate min −1 mg protein 1 ) occurred when external NH 4 + concentration was low (1 mM). L‐Methionine DL sulphoximine (MSX), a specific inhibitor of GS, inhibited uptake of 15 NH 4 Cl in 13‐d‐old mycelium of P. ericae. The nitrogen nutrition of the fungus and the host in the soil environment is discussed.