Inhibitory kinetics of chlorocinnamic acids on mushroom tyrosinase

Abstract

Tyrosinase (EC 1.14.18.1) is the key enzyme of most food enzymatic oxidation. Tyrosinase inhibitors are important in food industry. In the present paper, 2-chlorcinnamic acid and 2,4-dichlorocinnamic acid were synthesized and the inhibitory kinetics on mushroom tyrosinase were investigated. The results showed that both compounds synthesized could inhibit tyrosinase activity. For monophenolase activity, both chlorocinnamic acids could extended the lag time and decrease the steady-state activities, 2-chlorcinnamic acid extended the lag time just by 5%, and 2,4-dichlorcinnamic acid extended the lag time more than by 30.4%. For diphenolase activity, the IC50 values of 2-chlorcinnamic acid and 2,4-dichlorocinnamic acid were determined to be 0.765 mM and 0.295 mM, respectively. The inhibition kinetics showed that 2-chlorcinnamic acid and 2,4-dichlorocinnamic acid displayed a reversible and uncompetitive mechanism. The inhibition constants were determined to be 0.348 mM and 0.159 mM, respectively. The research may supply the basis for designing new tyrosinase inhibitors.

Keywords: Chlorcinnamic acid; DMSO; IC(50); Inhibition; K(IS); Kinetics; Mushroom tyrosinase; Synthesis; dimethyl sulfoxide; equilibrium constant of the inhibitor combining with the enzyme-substrate complex; l-3,4-dihydroxyphenylalanine; l-DOPA; l-Tyr; l-tyrosine; the inhibitor concentrations leading to 50% activity lost.