Influence of Oxidative and/or Reductive Treatment on Human Hair (III): Oxidative Reaction of Polyphenol Oxidase (Laccase) to Hair Dyeing

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We estimated levels of hair coloring and the oxidation-reduction potential (ORP) of laccase and dye precursors using cyclic voltammetry in an enzyme reaction system to understand the capability and characteristics of enzyme kinetics of polyphenol oxidase (laccase) in relation to hair dyeing. We also analyzed the correlation between these two parameters. We additionally compared the parameters of enzyme kinetics with combinations of laccase and several different dye precursors. Laccase exhibited superior capability over hydrogen peroxide (H₂O₂) in both the dye polymerization and hair-coloring tests. However, additional H₂O₂ was stoichiometrically higher than additional laccase in the enabled number of oxidative reactions. In addition, we evaluated the ORP of laccase and the dye precursors and observed a correlation between the strength of hair dyeing and the differences in the value of ORP in laccase and the dye precursors (ΔE). Furthermore, we measured the parameters of the enzyme kinetics in the reaction of laccase with several different dye precursors. Catalytic constant, k_cat, tended to correlate with the strength of hair dyeing and the difference of ORP in laccase and the dye precursors. Laccase demonstrated a superior capability for hair dyeing and the enzymatic reaction generated no H₂O₂. Additionally, the strength of hair dyeing correlated with ΔE, and tended to correlate with k_cat.