[Equilibrium and kinetic parameters of the interaction of peroxidase and its conjugates with specific antibodies in solution].

Horseradish peroxidase (HRP) and its conjugates with IgG (HRP-IgG) and cortisol (HRP-COR) interactions with polyvalent antibodies against peroxidase (ANTI-HRP) have been studied by homogeneous enzyme immunoassay. The total catalytic activity in o-phenylenediamine oxidation for free peroxidase or its conjugates and their immunocomplexes with antibodies against the enzyme (ANTI-HRP) has been measured. Linearization of time dependencies of the initial rate for peroxidation in the ln (v-v infinity)-time coordinates, where v and v infinity are the reaction rates at a definite moment of time and after the onset of the equilibrium, as well as in the [ANTI-HRP]/(v-v infinity)-[ANTI-HRP]0 and I/[ANTI-HRP]0k1 + k-1)-[ANTI-HRP]0 made it possible to determine the dissociation constant, Kd, and rate constant for the formation and dissociation, for the immunocomplexes k1 and k-1. The Kd values were in good agreement with those determined by the classical Scatchard method.