Stabilities and rates in the laccase/TEMPO-catalyzed oxidation of alcohols

The influence of alcohol, 4-acetylamino,2,2,6,6'-tetramethylpiperidinyloxy (4-acetylamino-TEMPO) and laccase (from Trametes versicolor, TvL) concentration in the aerobic oxidation of furfuryl alcohol was investigated. Studies show that the K-m for 4-acetylamino-TEMPO is around 6.3 mM (V-max=0.18 mM min(-1)) using 6.6 U mL(-1) of laccase and a furfuryl alcohol concentration of 140 mM. Under these optimized conditions, the reaction rate is still dependent on the concentration of enzyme in solution. Laccase can be reused, with a residual activity of around 25%. An important conclusion is that laccase is not stable in the presence of oxoammonium salts, presumably due to degradation via oxidation of essential amino acid residues or the glycosyl moieties on the periphery of the enzyme.