Electrode reactions of catechol at tyrosinase-immobilized latex suspensions

Tyrosinase was immobilized on polystyrene latex particles in order to control amounts of the enzyme. The tyrosinase-coated latex particles were composed of the core polystyrene and four successive coating layers: polystyrene sulfonate, polyallylamine, tyrosinase and polyallylamine again, built up by the layer-by-layer technique. They showed catalytic currents for the enzymatic oxidation of catechol to o-quinone. The enzyme activity per particle was evaluated as 2.3 × 10^-7 units from UV absorption of o-quinone. The relation between the catalytic current and the concentration of catechol leads to a Michaelis-Menten type kinetic equation. The layer-by-layer method was found to have a deactivating effect on enzyme catalysis. In spite of this, the catechol oxidation current was larger than the current from free tyrosinase at a common value of enzyme units per volume. This is ascribed to strong adsorption of the latex particles on the electrode, leading to the enhancement of the local concentration of tyrosinase.