Immobilisation and Kinetic Study of Tyrosinase for Biosensor Construction

ABSTRACT

The catalytic properties and stability of soluble and immobilised in nylon-6,6 mesh tyrosinase were studied with the help of an oxygen sensor. A variety of methods were examined for the immobilisation of tyrosinase, although active immobilised enzyme was obtained only with the help of benzidine and dicyclohexylcarbodiimide. The immobilisation caused an increase in the K_m value for catechol almost 2 times in comparison with that found for soluble enzyme (0.39 and 0.22 mM, respectively). The immobilised tyrosinase retained sufficient activity for several months. Due to its characteristic suicide inactivation induced by catechol, it is only of single use for analytical purposes.

Obtained data were also used for evaluation of the model of oximeter-based biosensors. This model allows the calculation of steady-state parameters from transient state data, excluding the influence of accompanying side processes; for tyrosinase-bound biosensors it gave very reproducible results for automatic data processing.

Keywords::

• tyrosinase
• immobilisation
• catalytic properties
• stability
• tyrosinase-bound biosensor
• calibration