This investigation, in vitro, shows that ozagrel, an antithrombotic drug, inhibited both monophenolase and diphenolase activities of mushroom tyrosinase when l-tyrosine and l-DOPA were assayed spectrophotometrically, respectively. The IC50 values, for monophenolase and diphenolase activities, were 1.35 and 3.45 mM, respectively. Ozagrel was estimated to be a reversible mixed-type inhibitor of diphenolase activity with the constants (KS1, KS2, Ki1, and Ki2) determined to be 2.21, 3.89, 0.454, and 0.799 mM, repectively. Increasing ozagrel concentrations provoked longer lag periods as well as a concomitant decrease in the monophenolase activity. Inhibition experiment demonstrated that ozagrel bound the enzyme at a site distincted from the substrate active site, but it bound to either E (Enzyme) or ES (Enzyme-Substrate) complex.
The inhibition concentration leading to 50% of enzyme activity lost
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The present investigation was supported by Esquel Group, Grant 50773009 of Natural Science Foundation of China, Grant IRT0526 of program for Changjiang Scholars and Innovative Research Team in university, UK-CHINA Joint Laboratory for Therapeutic Textiles, and Grant of B07024 of Biomedical Textile Materials ‘111 Project’ from Ministry of Education of China.