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Regulation of glutamate dehydrogenase activity by manipulation of nucleotide supply in Daucus carota suspension cultures
Author(s) -
Athwal Gurdeep S.,
Pearson John,
Laurie Sophie
Publication year - 1997
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1997.tb01030.x
Subject(s) - glutamate dehydrogenase , psychological repression , biochemistry , enzyme assay , nucleotide , daucus carota , adenosine , biology , enzyme , glutamate receptor , gene expression , botany , gene , receptor
The enzyme glutamate dehydrogenase (GDH, EC 1.4.1.2) is ubiquitous in plant species. It is now generally accepted that the primary role of this enzyme is not assimilation of ammonium and it has been suggested that GDH may be important in provision of carbon skeletons under conditions of carbon limitation. In carrot ( Daucus carota L. Chantenay) cell suspension cultures carbon starvation results in de‐repression of GDH activity. The regulation of this de‐repression has not been investigated. This paper examines the possibility that the availability of adenosine nucleotides is instrumental in the regulation of GDH activity. In repressed cultures the adenosine nucleotides cAMP (0.2 m M ), AMP (0.2 m M ) and ADP (0.4 m M ) caused an increase in GDH activity of 61, 33 and 7%, respectively. ATP (0.2 m M ) had the opposite effect in maintaining repression of GDH. Under de‐repressed conditions only cAMP (0.2 m M ) enhanced GDH activity (14%). Inhibition of oxidative phosphorylation using a range of inhibitors resulted in de‐repression of GDH and stimulation of respiration. The results from this work indicate that exogenously applied adenosine nucleotides and electron transport inhibitors alter the GDH repression/de‐repression status. Addition of these compounds alters or disrupts ATP levels, mimicking carbon depletion. This causes an increase in GDH activity, supporting the idea that GDH may provide carbon skeletons for carbon metabolism and suggesting that ATP status is important in regulation of the enzyme activity.