Effects of Ionic Liquids on Laccase from Trametes versicolor

Aashka Y Patel,Nicholas J Paradis,Meeraj Amin,Gregory A Caputo,Timothy D Vaden,Austin K Clark,Chun Wu

doi:10.3390/biophysica1040031

Abstract

Interactions between ionic liquids and biomolecules are of great interest due to the intrinsic properties of ionic liquids and the flexibility allowed by mixing and matching cations and anions to create unique ionic liquids. A number of ionic liquid–biomolecule studies have focused on interactions with proteins, including industrially relevant enzymes. One of these, laccase from Trametes versicolor, is a naturally derived enzyme used in the breakdown of phenolic compounds in a wide variety of industries, especially useful in breakdown of lignocellulosic materials. Here, a combination of experiments and molecular dynamics (MD) simulations was used to investigate the interactions of ionic liquids with laccase. Enzyme kinetics assays indicated that ionic liquids composed of tetramethylguanidine (TMG) and either serine or threonine caused significant reduction in enzymatic activity, while kinetics was not impacted by TMG-Asp or TMG-Glu ionic liquids. Similarly, intrinsic fluorescence of laccase in the presence of TMG-Ser and TMG-Thr exhibited a shift in spectral properties consistent with structural destabilization, but again TMG-Asp and TMG-Glu had no impact. MD simulations of laccase and ABTS with/without TMG-Ser ionic liquid provided insight into the deactivation mechanism of laccase. The simulations indicated that TMG-Ser disrupts laccase’s electron transfer mechanism.

Highlights

Ionic liquids (ILs) have been an attractive and dynamic topic of investigation in the fields of analytical chemistry and electrochemistry over the past 15–20 years
The enzymatic activity of the protein was characterized in the presence of either imidazolium ILs EMI-Cl, BMI-Cl, HMI-Cl, OMI-Cl or amino acid ILs TMG-Ser, TMG-Thr, TMG-Asp, TMG-Glu (Figure 1D)
The imidazolium ILs vary in the length of the alkyl group attached to the imidazole ring and have been shown to exert differing levels of protein destabilizing activity based on that alkyl chain length [22,23,41]

Summary

Introduction

Ionic liquids (ILs) have been an attractive and dynamic topic of investigation in the fields of analytical chemistry and electrochemistry over the past 15–20 years This interest stems from the many unique and interesting properties of ionic liquids (aka roomtemperature ionic liquids), including low to negligible vapor pressure, high conductivity, non-flammability, and high thermal stability [1]. These properties have made ILs of immediate interest in studies of energy storage and conduction, as well as a variety of other electrochemical applications [2,3,4]. The conductivity of ILs makes them ideal candidates for processes involving redox reactions while the low vapor pressure and thermal stability allow for improved recycling of these agents between processes [9,11,12,13]

Methods

Results

Discussion

Conclusion