Effect of Luteolin on Activity and Conformation of Tyrosinase
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Abstract:
The effects of luteolin on inhibitory action, inhibitory type and inhibitory kinetics of tyrosinase were investigated using the method of enzyme inhibition kinetics in 37 ℃, pH 6.8 sodium phosphate buffer (100 mmol/L) system, the changes of surface hydrophobicity and secondary structure of tyrosinase were also probed. The results showed that luteolin was a reversible and noncompetitive inhibitor (the half inhibition concentration (IC50) and inhibition constant (Ki) were obtained to be 55.35 μg/mL and 63.57 μg/mL, respectively). The time-courses analysis of inactivation kinetics indicated that luteolin interacted with tyrosinase quickly and inhibited the acticity of enzyme rapidly. Fluorescence spectrum analysis showed that luteolin significantly increased the surface hydrophobicity of tyrosinase. Circular dichroism spectra analysis showed the binding of luteolin to tyrosinase induced the unfolding of conformation and the gradual increase of α-helix content of tyrosinase (from 31.3% to 41.6%). The results of spectra analysis indicated that the binding of luteolin to tyrosinase altered the conformation of tyrosinase which was not conducive to the formation of active center, thereby reducing the activity of tyrosinase.
