Activity, Stability, and Structure of Native and Modified by Woodward Reagent K Mushroom Tyrosinase

Abstract

Mushroom tyrosinase (MT) was considered a good model for studying the inhibition, activation, and mutation of tyrosinase as the key enzyme of melanogenesis. In the present study, the activity, structure, reduction, and stability of native and modified enzymes were investigated after the modification of MT carboxylic residues by the Woodward reagent K (WRK). The relative activity of the sole enzyme was reduced from 100 to 77.9, 53.8, 39.4, and 26.4% after its modification by 2.5, 5, 25, and 50 ratios of [WRK]/[MT], respectively. The Tm values were calculated from thermal denaturation curves at 61.2, 60.1, 58.3, 53.9, and 45.5°C for the sole and modified enzymes. The reduction of the ΔGH2O values for the modified enzyme in chemical denaturation indicated instability. A structural study by CD and intrinsic fluorescence technique revealed the fluctuation of the secondary and tertiary structures of MT. Keywords: modification, mushroom tyrosinase, Woodward’s reagent K, kinetics, structure.