Loss of PII-dependent control of arginine biosynthesis in Dunaliella salina.

In cyanobacteria and most Archaeplastida, Arg regulates its formation via allosteric inhibition of the controlling enzyme, N-acetyl-L-glutamate kinase (NAGK) that requires PII protein to properly sense the feedback inhibitor. Although PII expression has been shown to be reduced in Dunaliella salina compared to other green algae, the potential impact of this protein on DsNAGK activity remains unclear. We here performed coupled enzyme assay and surface plasmon resonance analysis and show that DsNAGK is activated by NAG and inhibited by Arg but is not controlled by DsPII.

N-Acetyl-L-glutamate Kinase of : In Vivo Regulation by PII Protein and Beyond.

N-Acetyl-L-glutamate kinase (NAGK) catalyzes the rate-limiting step in the ornithine/arginine biosynthesis pathway in eukaryotic and bacterial oxygenic phototrophs. NAGK is the most highly conserved target of the PII signal transduction protein in Cyanobacteria and Archaeplastida (red algae and Chlorophyta). However, there is still much to be learned about how NAGK is regulated in vivo.