Laccase from Cerrena unicolor was immobilised in thin silicate film deposited on gold electrode. This film was obtained by sol-gel process from tetramethoxysilane - 0.01 M phospahte buffer based sol containing dissolved enzyme. The ezyme imbeded into the hydrophilic silicate matrix exhibit catalytic activity towards dioxygen reduction to water in the presence of mediator: 2,2'-azino-bis-(3-ethylbenzo- thiazoline-sulfonic acid) (ABTS).

This catalytic effect is pH and temperature dependent. The highest performance of the enzyme is found in solution of pH 4.5 ± 0.5. The catalytic behaviour of the system depends also on time elapsed after electrode immersion into buffer solution. The higher pH the longer time is requred to observe maximal catalytic activity of laccase towards dioxygen reduction. In solution of pH 4.5 the maximal activity is obatained in 24 hours. In more basic solutions time elapsed to obtain highest activity increases to 70 - 120 hours.

The maximum activity of the enzyme was found in teperature range 40ºC - 65ºC. The temperature dependence of the catalytic current can be described by Arrhenius equation in temperature range (15 - 40ºC). However, at temperature higher than 50ºC deviations form Arrhenius plot probably because of enzyme denaturation.