EFFECT OF SHORT-CHAIN ALKANOLS ON ENZYMATIC-ACTIVITY OF LACCASE FROM PHLEBIA-RADIATA VARIATIONS OF THE SUBSTRATE-BINDING CONSTANT

Laccase was isolated from the culture media of white-rot fungus Phlebi a radiata and purified. The effect of ethanol and methanol on oxidatio n of syringaldazine and 2,6-dimethoxyphenol was studied and described using the Michaelis-Menten equation. The turnover number of the enzyme was little dependent on alkanol addition over a relatively wide range of concentrations (to about 15% v/v ethanol). The binding constant, K -m, increased with addition of alkanols, first linearly, then - faster . A consistent description of the data obtained under non-denaturing c onditions was achieved using the model of competitive laccase inhibiti on by added alkanols. Interpretation of the data in terms of the effec tive chemical activity of water was also addressed.