ut am ate ▁in ▁un aden yl ated ▁G S . ▁The ▁four ▁am ino ▁ac ids ▁bind ▁to ▁the ▁site ▁by ▁their ▁common ▁atoms , ▁“ the ▁main ▁chain ” ▁of ▁am ino ▁ac ids . ▁Gl ut am ate ▁is ▁another ▁product ▁of ▁gl ut am ine ▁met abol ism ; ▁however , ▁gl ut am ate ▁is ▁a ▁substr ate ▁for ▁G S ▁in hib iting ▁it ▁to ▁act ▁as ▁a ▁reg ulator ▁to ▁G S . 2 ▁Each ▁in hib itor ▁can ▁reduce ▁the ▁activity ▁of ▁the ▁en zym e ; ▁once ▁all ▁final ▁gl ut am ine ▁met abol ites ▁are ▁bound ▁to ▁G S , ▁the ▁activity ▁of ▁G S ▁is ▁almost ▁completely ▁in hib ited . ▁Many ▁in hib itory ▁input ▁signals ▁allows ▁for ▁fine ▁tun ing ▁of ▁G S ▁by ▁reflect ing ▁nit ro gen ▁levels ▁in ▁the ▁organ ism . ▁ ▁Fe ed back ▁reg ulation ▁distingu ishes ▁the ▁difference ▁between ▁two ▁e uk ary otic ▁types ▁of ▁G S : ▁brain ▁and ▁non - bra in ▁t issues . ▁Non - bra in ▁G S ▁respond s ▁to ▁end - product ▁feedback ▁in hib ition , ▁while ▁brain ▁G S ▁does ▁not . ▁ ▁High ▁concentr ations ▁of ▁gl ut am ine - dependent ▁met abol ites ▁should ▁in hib it ▁G S ▁activity , ▁while ▁low ▁concentr ations ▁should ▁activ ate ▁G S ▁activity . ▁ ▁In hib itors : ▁ ▁M eth ion ine ▁sul fo xim ine ▁( MS O