Application of a sensitive catechol detector for determination of tyrosinase inhibitors

A substrate regenerating bienzyme sensor was used to measure a variety of organic and inorganic inhibitors with high sensitivity. The bienzyme system consists of the two cooperating enzymes, cytosolic quinoprotein glucose dehydrogenase and mushroom tyrosinase. The cooperation takes place on the substrate/product level. Under kinetic control, compounds that affect one of the enzymes can be detected with high sensitivity. For the construction of the sensor, the enzymes were immobilized in polyvinyl alcohol, coupled to a Clark-type oxygen electrode and the oxygen consumption was monitored during catechol conversion. In this way, carboxylic acids, kojic acids, inorganic ions and thiourea derivatives were studied. Theoretical considerations reveal the relationship between amplification gain and inhibitor concentration.