Activation kinetics of tyrosinase catalyzing reaction by caffeic acid

Enzyme activation was of significance to the biological or enzymatic treatment of organic wastewaters. The activation effects of caffeic acid on the activity of monophenolase and diphenolase contained in tyrosinase were studied by enzymological kinetic method. Caffeic acid was found to activate the monophenolase and diphenolase activity of tyrosinase. The caffeic acid concentration leading to 50% activation rate (ACSO) were 0.27 mmol/L for monophenolase activity and 1.35 mmol/L for diphenolase activity. Caffeic acid can remove the lag time of tyrosinase for oxidation of L-tyrosine. The activation kinetics analyzed by Lineweaver-Burk plots found caffeic acid to be a competitive activator for the oxidation of L-DOPA. The Michaelis constants, Km, are 0.73, 0.48, 0.33 and 0.15 mmol/L when the concentration of caffeic acid are 0, 0.50, 1.0 and 1.5 mmol/L respectively.