▁col i ▁en zym e ▁as part ate ▁car b amo yl trans fer ase ▁( AT Case ) ▁ ▁has ▁become ▁another ▁good ▁example ▁of ▁al loster ic ▁reg ulation . ▁ ▁The ▁kin etic ▁properties ▁of ▁al loster ic ▁en zym es ▁are ▁often ▁explained ▁in ▁terms ▁of ▁a ▁conform ational ▁change ▁between ▁a ▁low - activity , ▁low - aff inity ▁" ten se " ▁or ▁T ▁state ▁and ▁a ▁high - activity , ▁high - aff inity ▁" relax ed " ▁or ▁R ▁state . ▁ ▁These ▁struct ur ally ▁distinct ▁en zym e ▁forms ▁have ▁been ▁shown ▁to ▁exist ▁in ▁several ▁known ▁al loster ic ▁en zym es . ▁ ▁However ▁the ▁mole cular ▁basis ▁for ▁conversion ▁between ▁the ▁two ▁states ▁is ▁not ▁well ▁understood . ▁ ▁Two ▁main ▁models ▁have ▁been ▁proposed ▁to ▁describe ▁this ▁mechanism : ▁the ▁" con cert ed ▁model " ▁of ▁Mon od , ▁W yman , ▁and ▁Change ux , ▁and ▁the ▁" sequ ential ▁model " ▁of ▁K osh land , ▁Nem eth y , ▁and ▁Fil mer . ▁ ▁In ▁the ▁concert ed ▁model , ▁the ▁protein ▁is ▁thought ▁to ▁have ▁two ▁“ all - or - none ” ▁global ▁states . ▁▁ ▁This ▁model ▁is ▁supported ▁by ▁positive ▁co oper ativity ▁where ▁binding ▁of ▁one ▁lig and ▁increases ▁the ▁ability ▁of ▁the ▁en zym e ▁to ▁bind ▁to ▁more ▁lig ands . ▁The ▁model ▁is ▁not ▁supported ▁by ▁negative ▁co oper ativity ▁where ▁losing ▁one ▁lig and ▁makes ▁it