Activation and coupling of the glutaminase and synthase reaction of glutamate synthase is mediated by E1013 of the ferredoxin-dependent enzyme, belonging to loop 4 of the synthase domain

Ferredoxin-dependent glutamate synthase (FdGltS), 2-oxoglutarate (2-OG) and L-glutamine (L-Glu) contribute to the activation of the glutaminase site and to ammonia transfer through the tunnel in a two step process. This process requires partial activation upon binding of 2-OG at the synthase site, followed by full activation brought about by glutamine binding.