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Study of the Kinetics of Oxidation of Monophenols by Tyrosinase. The Effect of Reducers

G. S. Gukasyan

Armenian Scientific Research Institute of Applied Chemistry (ARIAC), ul. Bagratuniants 70, Yerevan, 375029 Armenia; fax: (3741) 562-465; E-mail: bio@arminco.com

Received July 5, 2000; Revision received May 29, 2001
Kinetics of oxidation of monophenols by tyrosinase from the fungus Aspergillus flavipes 56003 and the effect of Fe2+, serine, and ascorbic acid on this reaction were studied. The effectors were shown to accelerate the oxidation of monophenols, decreasing the lag-time of the reaction. It is assumed that the activation of the tyrosinase in the presence of Fe2+ is due to a direct reduction of the active site copper ions. Serine and ascorbic acid are supposed to affect the reaction of quinone transformation. The activation of the enzyme in the presence of Fe2+ suggests that the oxidation of monophenols is an autocatalytic process.
KEY WORDS: tyrosinase, Aspergillus, kinetics