Inhibitory Effects of Some Flavonoids on the Activity of Mushroom Tyrosinase

Li-Ping Xie¹, Qing-Xi Chen², Huang Huang², Hong-Zhong Wang¹, and Rong-Qing Zhang^1*

¹Department of Biological Science and Biotechnology, Center for Ocean Science and Engineering, Protein Science Laboratory of Ministry of Education, Tsinghua University, Beijing 100084, The People's Republic of China; fax: (8610) 6277-2899; E-mail: rgzhang@mail.tsinghua.edu.cn

²The Key Laboratory of Ministry of Education for Cell Biology and Tumor Cell Engineering, Department of Biology, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China

^* To whom correspondence should be addressed.

Received June 18, 2002; Revision received August 21, 2002

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Mushroom tyrosinase (EC 1.14.18.1) is a copper containing oxidase that catalyzes both the hydroxylation of tyrosine into o-diphenols and the oxidation of o-diphenols into o-quinones, and then forms brown or black pigments. In the present study, the effects of some flavonoids on the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) have been studied. The results show that flavonoids can lead to reversible inhibition of the enzyme. A kinetic analysis showed that the flavonols are competitive inhibitors, whereas luteolin is an uncompetitive inhibitor. The rank order of inhibition was: quercetin > galangin > morin; fisetin > 3,7,4´-trihydroxyflavone; luteolin > apigenin > chrysin.

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KEY WORDS: mushroom tyrosinase, flavonoids, inhibitory mechanism

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