Comparison of catalytic performance of haloalkane dehalogenases in deep eutectic and organic co-solvents

Radka Chaloupkova¹, Veronika Stepankova^1,2, Pavel Vanacek¹, and Jiri Damborsky^1,2

¹Loschmidt Laboratories, Department of Experimental Biology and Research Centre for Toxic Compounds in the Environment, Faculty of Science, Masaryk University, Brno

²International Clinical Research Center, St. Anne's University Hospital Brno, Brno

radka@chemi.muni.cz

Haloalkane dehalogenases (HLDs, EC 3.8.1.5) make up an important class of enzymes that cleave carbon-halogen bonds in a broad range of halogenated aliphatic compounds with potential utilization in biodegradation, biocatalysis and biosensing [1]. Application potential of HLDs could be further improved by adding appropriate co-solvent to the reaction media, leading to enhanced solubility of their hydrophobic substrates and suppression of the substrates spontaneous hydrolysis. Here we focus on biotransformation by HLDs in the presence of novel and green deep eutectic solvent ethaline, consisting of ethylene glycol and choline chloride [2]. Catalytic performance of three haloalkane dehalogenases, DbjA, DhaA and LinB, in aqueous solutions of ethaline was systematically and critically compared with the enzyme reactivity in the presence of the individual components of ethaline and two conventional organic solvents, methanol and acetone [3]. The activities of studied enzymes responded differently to the different co-solvents. All of the enzymes tolerated ethaline and ethylene glycol significantly better than methanol and acetone. Haloalkane dehalogenase DhaA was found to be the most tolerant of ethaline. Its excellent compatibility with the solvent was demonstrated by the enzyme’s enhanced thermal stability, and by its retention of detectable catalytic activity even at very high ethaline concentrations (≥ 90% v/v). In contrast, the activities of DbjA and LinB were higher in ethylene glycol than in ethaline. Moreover the activity of DbjA was 1.5 times higher in 50% (v/v) ethylene glycol than in a pure buffer. Additionally, the enantioselectivity of DbjA increased more than 4-fold in the presence of ethaline or ethylene glycol. Our results demonstrate that ethylene glycol and deep eutectic solvent ethaline can have beneficial effects on catalysis by haloalkane dehalogenases, broadening their usability in “green” biotechnologies.

[1] T. Koudelakova, S. Bidmanova, P. Dvorak, A. Pavelka, R. Chaloupkova, Y. Prokop & J. Damborsky, Biotechnology Journal 8 (2013) 32-45.

[2] A. P. Abbott, G. Capper, D. L. Davies, R. K. Rasheed, & V. Tambyrajah, Chemical Communications 1 (2003) 70-71.

[3] V. Stepankova, P. Vanacek, J. Damborsky & R. Chaloupkova, Green Chemistry DOI:10.1039/C4GC00117F