Role of Glutamine Synthetase in Plant Nitrogen Metabolism

Role of Glutamine Synthetase in Plant Nitrogen Metabolism 

Amongst the plant enzymes that use ammonia as substrate, glutamine synthetase (GS E.C. 6.3.1.2) has the highest affinity (Km 3-5 pm) for this nitrogen source. Ammonia is released in plant tissues by nitrite redudion and amino acid catabolism but the highest amount, up to 90%, originates in photosynthetic tissues from the photorespiratory C2 cycle [1]. 

Twtophan Asparagine Ureides Histidine / Nucleic acids 

GS2 deficient barley mutants isolated under conditions that suppress photorespiration grow without phenotypic aberrations under nonphotorespiratory conditions (2% O2, 0.7% GO2), but mutants with less than 40% of the wild-type GS2 activity show severe phytotoxic symptoms, mainly chlorophyll destruction, when 

These mutants demonstrate that glutamine synthetase is a potential target for herbicidal compounds and they indicate that photosynthetic tissue is most vulnerable for herbicidal damage caused by GS inhibitors. 

---