RT Journal Article SR Electronic(1) A1 BOGONEZ, ELENA A1 SATRÚSTEGUI, JORGINA A1 MACHADO, ALBERTOYR 1985 T1 Regulation by Ammonium of Glutamate Dehydrogenase (NADP+) from Saccharomyces cerevisiae JF Microbiology, VO 131 IS 6 SP 1425 OP 1432 DO https://doi.org/10.1099/00221287-131-6-1425 PB Microbiology Society, SN 1465-2080, AB The activity of glutamate dehydrogenase (NADP+) (EC 1.4.1.4; NADP-GDH) of Saccharomyces cerevisiae is decreased under conditions in which intracellular ammonia concentration increases. A high internal ammonia concentration can be obtained (a) by increasing the ammonium sulphate concentration in the culture medium, and (b) by growing the yeast either in acetate + ammonia media, where the pH of the medium rises during growth, or in heavily buffered glucose + ammonia media at pH 7·5. Under these conditions cellular oxoglutarate concentrations do not vary and changes in NADP-GDH activity appear to provide a constant rate of oxoglutarate utilization. The following results suggest that the decrease in NADP-GDH activity in ammonia-accumulating yeast cells is brought about by repression of synthesis: (i) after a shift to high ammonium sulphate concentrations, the number of units of activity per cell decreased as the inverse of cell doubling; and (ii) the rate of degradation of labelled NADP-GDH was essentially the same in ammonia-accumulating yeast cells and in controls, whereas the synthesis constant was much lower in the ammonia-accumulating cells than in the controls., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-131-6-1425