Study of the inhibition of 3-/4-aminoacetophenones on tyrosinase
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When the action of tyrosinase on l-dopa in the presence of 3-aminoacetophenone is studied, inhibition or activation is observed depending on the concentration of substrate. These opposing effects are due to non-enzymatic reactions: when tyrosinase acts on l-dopa, a highly reactive molecule, o-dopaquinone, originates, which evolves to dopachrome; in the presence of 3-/4-aminoacetophenones, the amino group of these compounds nucleophilically attacks the o-quinones, generating a colorless adduct, which, in turn, is oxidized by another molecule of o-dopaquinone, giving a colored compound with an absorbance higher than that of the dopachrome in an apparent activating effect. Therefore, an apparent activation or inhibition is seen depending on the concentration of l-dopa used in the experiments. Moreover, docking studies showing the binding mode of these molecules to the met (E m) and oxy (E ox) forms of tyrosinase reveal that both compounds arranges itself in the active centre in a similar way to monophenolic substrates of the enzyme, confirming the inhibition of the enzyme. We proposed a kinetic test to elucidate whether a compound is a true activator or an inhibitor of tyrosinase.
Keywords3-Aminoacetophenone 4-Aminoacetophenone Tyrosinase Activation Inhibition
This work was partially supported by grants from several Spanish organizations: Projects 19545/PI/14, 19304/PI/14 and 19240/PI/14 (Fundación Seneca, CARM, Murcia, Spain); Projects SAF2013-48375-C2-1-R and CTQ2014-56887-P (MINECO, Madrid); Projects UMU15452 and UMU17766 (University of Murcia, Murcia); C.V. Ortiz-Ruiz has a MEC-FPU fellowship (AP2010-4300), A. Garcia-Jimenez has a FPU fellowship from University of Murcia.
Compliance with ethical standards
Conflict of interest
All authors declare no competing financial interest.
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