KINETICS OF HOMEOSTATIC BEHAVIOR OF RECEPTOR-ENZYME SYSTEMS UNDER THEACTION OF PHYSIOLOGICALLY ACTIVE COMPOUNDS

We describe two types of models. In the first one it is assumed that r egulation of enzyme activity occurs by the product of the enzyme react ion. In the second it is assumed that concomitant action of ligand occ urs on at least two targets with opposite effects (dual-action model). Kinetic analysis of models of the first type shows that homeostatic r esponse with respect to the key metabolite of the receptor-enzyme syst em is possible only if the enzyme kinetics are described by the equati on of zero order. In 'dual-action' models, the homeostatic behavior of the system is defined by the mechanisms of compensation of the ligand primary effect. (C) 1998 Elsevier Science Ireland Ltd.