Regulatory enzymes whose catalytic activity is modulated by the noncovalent binding of a specific metabolite (effector) at a site (regulatory site) other than the catalytic site (on the enzyme). Effector binding causes a three-dimensional conformation change in the enzyme and is the root of the modulation. The term is used to differentiate this form of regulation from the type that may result from the competition between substrate and inhibitors at the catalytic site.
An enzyme whose activity can change when certain types of effectors, called allosteric effectors, bind to a nonactive site on the enzyme.