▁( object ). " ▁This ▁is ▁in ▁reference ▁to ▁the ▁fact ▁that ▁the ▁regul atory ▁site ▁of ▁an ▁al loster ic ▁protein ▁is ▁phys ically ▁distinct ▁from ▁its ▁active ▁site . ▁ ▁The ▁protein ▁catal yst ▁( enz yme ) ▁may ▁be ▁part ▁of ▁a ▁ ▁multi - sub unit ▁complex , ▁and / or ▁may ▁trans ient ly ▁ ▁or ▁perman ently ▁associate ▁with ▁a ▁C of actor ▁ ▁( e . g . ▁ad en os ine ▁tri ph osph ate ). ▁Catal ysis ▁of ▁bio chem ical ▁re actions ▁is ▁vital ▁due ▁to ▁the ▁very ▁low ▁reaction ▁rates ▁of ▁the ▁un catal ys ed ▁ ▁re actions . ▁A ▁key ▁driver ▁of ▁protein ▁evolution ▁is ▁the ▁optimization ▁of ▁such ▁catal yt ic ▁ ▁activities ▁via ▁protein ▁dynamics . ▁ ▁Where as ▁en zym es ▁without ▁couple d ▁domains / sub un its ▁display ▁normal ▁Michael is - M enten ▁k inet ics , ▁most ▁al loster ic ▁en zym es ▁have ▁multiple ▁couple d ▁domains / sub un its ▁and ▁show ▁co oper ative ▁binding . ▁ ▁Gener ally ▁speaking , ▁such ▁co oper ativity ▁results ▁in ▁al loster ic ▁en zym es ▁displaying ▁a ▁sig m oid al ▁dependence ▁on ▁the ▁concentration ▁of ▁their ▁substr ates ▁in ▁posit ively ▁co oper ative ▁systems . ▁This ▁allows ▁most ▁al loster ic ▁en zym es ▁to ▁greatly ▁vary ▁catal yt ic ▁output ▁in ▁response ▁to ▁small ▁changes ▁in ▁effect or ▁concentration . ▁E ff ector ▁mole cules , ▁which ▁may ▁be