CHANGES IN INTRACELLULAR AMINO-ACIDS AND GLUTAMINE - GLUTAMATE DURING N-DEPRIVATION AND FEEDING IN CANDIDA-NITRATOPHILA

In the yeast, Candida nitratophila Shifrine et Phaff, the intracellular concentrations of α‐amino acids decreased rapidly during N‐deprivation, with the ratio of glutamine: glutamate (Gln: Glu) falling from 07 in NH4+‐grown cells, or 0.5 in NO3−‐grown cells, to 0.1 after 1 h. Addition of NH4+ to N‐deprived cultures resulted in rapid increases in glutamate, glutamine and alanine with Gln: Glu exceeding 1.5 within 30 min. Recovery of other amino acids, such as arginine, was much slower. Addition of NO3, resulted in a less rapid increase in the concentration of some intracellular amino acids, including glutamate and glutamine, while levels of arginine continued to fall for 30 min after addition of this N‐source. Gln: Glu was slow to rise in NO3− pulsed cells. Addition of NH4+ to cells growing on NO3− produced little change over the following 2 h other than decreases in arginine and histidine. Carbon deprivation resulted in a rapid decrease in levels of glutamate, glutamine and alanine, but not of aspartate (which this yeast is unable to use as a sole C‐source for growth) or arginine. Gln: Glu increased during C‐deprivation but fell within 10 min to normal levels on addition of glucose. It is concluded that, in C. nitratophila, Gln:Glu values correlate well with C‐N status. Copyright © 1990, Wiley Blackwell. All rights reserved