▁G S ▁activity ▁in ▁r ats ▁by ▁the ▁use ▁of ▁M SO . ▁ ▁Class es ▁▁ ▁There ▁seem ▁to ▁be ▁three ▁different ▁classes ▁of ▁G S : ▁▁ ▁Class ▁I ▁en zym es ▁( G SI ) ▁are ▁specific ▁to ▁pro k ary otes , ▁and ▁are ▁o lig om ers ▁of ▁ 1 2 ▁identical ▁sub un its . ▁The ▁activity ▁of ▁G SI - type ▁en zym e ▁is ▁controlled ▁by ▁the ▁ad en yl ation ▁of ▁a ▁ty ros ine ▁resid ue . ▁The ▁ad en yl ated ▁en zym e ▁is ▁in active . ▁▁ ▁Class ▁II ▁en zym es ▁( GS II ) ▁are ▁found ▁in ▁e uk ary otes ▁and ▁in ▁b acter ia ▁belonging ▁to ▁the ▁Rh iz ob ia ceae , ▁Frank ia ceae , ▁and ▁Stre pt om yc et aceae ▁families ▁( th ese ▁b acter ia ▁have ▁also ▁a ▁class - I ▁G S ). ▁G S II ▁are ▁dec amer ▁of ▁identical ▁sub un its .. ▁ ▁Pl ants ▁have ▁two ▁or ▁more ▁is oz ym es ▁of ▁G S II , ▁one ▁of ▁the ▁is oz ym es ▁is ▁trans located ▁into ▁the ▁ch lor op last . ▁Another ▁form ▁is ▁c yt os ol ic . ▁The ▁c yt os ol ic ▁G S ▁gene ▁translation ▁is ▁reg ulated ▁by ▁its ▁ 5 ' ▁un trans l ated ▁region ▁( UT R ), ▁while ▁its ▁ 3 ' ▁U TR ▁plays ▁role ▁in ▁trans cript ▁turn over .