In the unicellular alga Cyanidium caldarium nitrate utilization is strongly inhibited by ammonium and it is resumed when ammonium has been depleted. In the presence of L‐methionine‐DL‐sulphoximine (MSX), which prevents ammonium assimilation through a specific irreversible inhibition of glutamine synthetase, nitrate reduction is no longer inhibited by ammonium, and most of the ammonium derived from nitrate reduction is excreted into the external medium. However, in the presence of MSX, nitrate reduction to ammonium proceeds at a reduced rate (45 to 70% of the control); this is particularly marked at low nitrate concentration. It is hypothesized that either MSX or accumulating ammonium bring about decrease in the rate of nitrate entry into the cell. Copyright © 1982, Wiley Blackwell. All rights reserved
Effect of L‐methionine‐DL‐sulphoximine, a specific inhibitor of glutamine synthetase, on ammonium and nitrate metabolism in the unicellular alga Cyanidium caldarium
FUGGI, Amodio;
1982
Abstract
In the unicellular alga Cyanidium caldarium nitrate utilization is strongly inhibited by ammonium and it is resumed when ammonium has been depleted. In the presence of L‐methionine‐DL‐sulphoximine (MSX), which prevents ammonium assimilation through a specific irreversible inhibition of glutamine synthetase, nitrate reduction is no longer inhibited by ammonium, and most of the ammonium derived from nitrate reduction is excreted into the external medium. However, in the presence of MSX, nitrate reduction to ammonium proceeds at a reduced rate (45 to 70% of the control); this is particularly marked at low nitrate concentration. It is hypothesized that either MSX or accumulating ammonium bring about decrease in the rate of nitrate entry into the cell. Copyright © 1982, Wiley Blackwell. All rights reservedI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
