ium ▁ion , ▁influ ences ▁gl ut am ine ▁synth esis ▁and ▁gl ut am ine ▁hydro ly s is . ▁Gl ut am ine ▁is ▁formed ▁if ▁an ▁am mon ium ▁ion ▁attacks ▁the ▁a cy l - ph osph ate ▁intermediate , ▁while ▁gl ut am ate ▁is ▁re made ▁if ▁water ▁attacks ▁the ▁intermediate . ▁ ▁Am mon ium ▁ion ▁bind s ▁more ▁strongly ▁than ▁water ▁to ▁G S ▁due ▁to ▁electro static ▁forces ▁between ▁a ▁c ation ▁and ▁a ▁neg atively ▁charged ▁pocket . ▁Another ▁possible ▁reaction ▁is ▁upon ▁N H 2 OH ▁binding ▁to ▁G S , ▁rather ▁than ▁N H 4 + , ▁yields ▁ γ - gl ut am yl h ydro x am ate . ▁ ▁Str ucture ▁▁ ▁Gl ut am ine ▁synth et ase ▁can ▁be ▁composed ▁of ▁ 8 , ▁ 1 0 , ▁or ▁ 1 2 ▁identical ▁sub un its ▁separated ▁into ▁two ▁face - to - face ▁rings . ▁B acter ial ▁G S ▁are ▁d ode cam ers ▁with ▁ 1 2 ▁active ▁sites ▁between ▁each ▁mon omer . ▁Each ▁active ▁site ▁creates ▁a ▁‘ t unnel ’ ▁which ▁is ▁the ▁site ▁of ▁three ▁distinct ▁substr ate ▁binding ▁sites : ▁nucle ot ide , ▁am mon ium ▁ion , ▁and ▁am ino ▁acid . ▁ATP ▁bind s ▁to ▁the ▁top ▁of ▁the ▁b if unnel ▁that ▁opens ▁to ▁the ▁external ▁surface ▁of ▁G S . ▁Gl ut am ate ▁bind s ▁at ▁the ▁bottom ▁of ▁the ▁active ▁site