Steady-state kinetics of lactoperoxidase with ABTS as chromogen.

A steady-state study of the oxidation of 2,2′ Azino-di-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) by purified lactoperoxidase has revealed complex kinetics as judged by non-hyperbolic initial velocity versus substrate concentration curves. The simplest rate equation that can account for this behaviour is of at least third degree and probably higher, as has been recently suggested for horse-radish peroxidase. In addition, evidence is presented which suggests that lactoperoxidase exists as an equilibrium mixture of monomers and aggregates.