Laccase-Mediator System Using a Natural Mediator as a Whitening Agent for the Decolorization of Melanin.

Saerom Park,Hyejin Do,Dahun Jung,Soeun Hwang,Dongjun Lee,Sang Hyun Lee,Jonghyeon Yun

doi:10.3390/polym13213671

Abstract

In this study, a laccase-mediator system (LMS) using a natural mediator was developed as a whitening agent for melanin decolorization. Seven natural mediators were used to replace synthetic mediators and successfully overcome the low redox potential of laccase and limited access of melanin to the active site of laccase. The melanin decolorization activity of laccases from Trametes versicolor (lacT) and Myceliophthora thermophila (lacM) was significantly enhanced using natural mediators including acetosyringone, syringaldehyde, and acetovanillone, which showed low cytotoxicity. The methoxy and ketone groups of natural mediators play an important role in melanin decolorization. The specificity constants of lacT and lacM for melanin decolorization were enhanced by 247 and 334, respectively, when acetosyringone was used as a mediator. LMS using lacM and acetosyringone could also decolorize the melanin present in the cellulose hydrogel film, which mimics the skin condition. Furthermore, LMS could decolorize not only synthetic eumelanin analogs prepared by the oxidation of tyrosine but also natural melanin produced by melanoma cells.

Highlights

Laccases (EC 1.10.3.2, benzenediol: dioxygen oxidoreductases) are multicopper proteins that catalyze the oxidation of various phenolic and non-phenolic compounds via a radical-catalyzed reaction mechanism by the reduction of molecular oxygen [1,2]
When the access of target compounds into the active site of laccase is limited by their steric hindrance, mediator radicals formed by laccase can efficiently oxidize the target compounds by the electron transfer or hydrogen atom transfer mechanism [12]
Syringaldehyde, and p-coumaric acid were used, the decolorization yields were 28%, 22%, and 18%, respectively, after 5 h of reaction. These results clearly demonstrate the usefulness of natural mediators for the melanin decolorization reaction by laccase-mediator systems (LMS)

Summary

Introduction

Laccases (EC 1.10.3.2, benzenediol: dioxygen oxidoreductases) are multicopper proteins that catalyze the oxidation of various phenolic and non-phenolic compounds via a radical-catalyzed reaction mechanism by the reduction of molecular oxygen [1,2]. Laccases have been used to catalyze the polymerization of dye precursors and organic compounds [11]. Their attractive properties, such as low substrate specificity, the use of oxygen as the final electron acceptor, generation of water as a by-product, and no demand (or no production) of peroxides, make them interesting in biotechnological and environmental fields [1,11,12]. The redox potential of the T1 site Cu is considered as a major factor in determining the catalytic ability of laccases [14]. Laccases cannot directly oxidize non-phenolic substrates with redox potential above 1.3 V [13,14]. To overcome the limitations of laccase, laccase-mediator systems (LMS) using small molecular compounds, such as 2,2 -azinobis(3ethylbenzthiazoline-6-sulphonate) (ABTS), 1-hydroxybenzotriazole (HOBt), violuric acid (VLA), N-hydroxyphthalimide (HPI), N-hydroxyacetanilide (NHA), and TEMPO, which act as redox mediators, have been suggested [15,16,17]

Methods

Results

Conclusion