Inhibitory effects of naphthols on the activity of mushroom tyrosinase

Tyrosinase (EC 1.14.18.1), a copper-containing multifunctional oxidase, was known to be a key enzyme for biosynthesis in fungi, plants and animals. In this work, the inhibition properties alpha-naphthol and beta-naphthol toward the activity of tyrosinase have been evaluated, and the effects of alpha-naphthol and beta-naphthol on monophenolase and diphenolase activity of tyrosinase have been investigated. The results showed that both alpha-naphthol and beta-naphthol could potently inhibit both monophenolase activity and diphenolase activity of mushroom tyrosinase, and that beta-naphthol exhibited stronger inhibitory effect against tyrosinase than alpha-naphthol. For monophenolase activity, beta-naphthol could not only lengthen the lag time but also decrease the steady-state activity, while alpha-naphthol just only decreased the steady-state activity. For diphenolase activity, both alpha-naphthol and beta-naphthol displayed revisible inhibition. Kinetic analyses showed that both alpha-naphthol and beta-naphthol were competetive inhibitors. (c) 2012 Elsevier B.V. All rights reserved.