Abstract:

The inhibitory effect of vanillin on the activities of monophenolase and diphenolase contained in tyrosinase was studied by means of the enzymological kinetic method in a Na₂HPO₄-NaH₂ PO₄ buffer solution with pH 6.8 at 25 ℃.The results show that the activities of both monophenolase and diphenolase are inhibited by vanillin.with the vanillin concentration leading to 50% of inhibitmy rate(IC5o)respectively being 2.7 and 4.1 mmol/L,that vanillin extends the lag time of monophenolase for oxidation from 1.1 to 3 min in a vanillin concentration of 4 mmol/L.and that the inhibitory efect of vanillin on diphenolase is in a mixed mode.which is proved by Lineweaver-Burk plots.Moreover,the inhibiting constants for the inhibitor binding with free enzyme and enzyme—substrate complex are respectively 3.48 and 15.1 mmo1/L.

Key words: words, vanillin, tyrosinase, activity, inhibitory efect, enzymological kinetics, monophenolase, dipheno, ase