Fig. 3
a Lineweaver–Burk plots for the inhibition of shikonin on mushroom tyrosinase for the oxidation of l-DOPA. b The plot of slope versus the concentration of shikonin for determining the inhibition constants KI. KI = 19 μmol/L. c The plot of intercept versus the concentration of shikonin for determining the inhibition constants KIS. KIS = 48.6 μmol/L.KI = equilibrium constant for inhibitor binding with free enzyme; KIS = enzyme–substrate complex; l-DOPA = l-3,4-dihydroxyphenylalanine