ISSN:
1399-3054
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Biologie
Notizen:
The involvement of three NAD(P)+-L-glutamate dehydrogenase (GDH; EC 1.4.1.3) isoenzymes, named GDH1, GDH2 and GDH3, in the carbon and nitrogen metabolism of the green alga Chlamydomonas reinhardtü 6145c has been investigated under different environmental and stress conditions. GDH1 activity decreased, but GDH2 and GDH3 activities increased with the age of cultures. When the extracellular ammonium concentration was high, only GDH1 activity increased with growth whereas GDH2 and GDH3 remained unchanged. In the presence of L-methionine-D,L-sulfoximine (MSX), an inhibitor of L-glutamine synthetase (GS), a significant increase of GDH1 and a slight decrease in GDH3 activity was observed, whereas GDH2 did not change. A significant increase in the intracellular 2-oxoglutarate was also found upon addition of azaserine, an inhibitor of L-glutamate synthase (GOGAT) activity. However, no significant changes in GDH isoenzyme activities were observed after addition of azaserine or azaserine plus MSX, except an induction of GDH3 in the latter case. Moreover, in the presence of ethoxyzolamide (ETZ), an inhibitor of carbonic anhydrase activity, an induction of total GDH activity, mainly due to an increase in GDH1 and to a minor extent in GDH2, was observed in cells under low CO2 (0.03%). In the dark, cells showed an increase in GDH1 activity, but when acetate was present GDH1 activity was repressed. All these results taken together suggest a relationship between GDH1 and nitrogen assimilation, whereas GDH2 and GDH3 seem to be involved in the production of 2-oxoglutarate to fuel the tricarboxylic acid (TCA) cycle.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1399-3054.1995.tb00967.x
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