Enantioselective conversion of 2,3-dichloropropanol by haloalcohol dehalogenase HheC: Design of non-selective catalyst

D. Bednář¹, P. Dvořák¹², Z. Prokop¹, J. Damborský¹², and J. Brezovský¹

¹Loschmidt Laboratories, Department of Experimental Biology and Centre for Toxic Compounds in the Environment, Faculty of Science, Masaryk University, Kamenice 5/A13, 625 00 Brno, Czech Republic;

² International Clinical Research Center, St. Anne's University Hospital Brno, Pekarska 53, 656 91 Brno, Czech Republic

222755@mail.muni.cz

TCP is widely used persistent contaminant with a carcinogenic and toxic effect on living organisms [1]. The conversion of 2,3-dichloropropanol (DCP) to corresponding epoxide is the second step in the dechlorination of 1,2,3‑trichloropropan (TCP) to glycerol [2]. The haloalcohol dehalogenase HheC [3] catalyses this second step in the TCP biodegradation pathway by cleaving-off the two remaining chlorine atoms of the DCP. However, the enantioselectivity of this reaction represents significant problem in the biodegradation pathway since after convertion of (R)-DCP, toxic (S)‑DCP accumulates in the solution.

Only limited knowledge about molecular principles of HheC enantioselectivity is available to date. Molecular docking and quantum mechanics calculations were therefore employed to provide detailed information about molecular basis of HheC enantioselectivity. Molecular docking revealed small preference in binding of (R)-DCP over (S)‑DCP, which corresponds well with experimental analysis. The two-step dehalogenation reaction was proposed for conversion of DCP based on quantum mechanical calculations, but no significant difference in the conversion of (R)- and (S)-DCP was observed at the level of employed theory. Results from molecular docking and quantum mechanics were complemented by FoldX calculations [4] to identify several hot spots for saturation mutagenesis. Experimental construction of mutants and their screening for enantioselectivity is currently on-going in our laboratory.

This work was financially supported by the European Regional Development Fund (CZ.1.05/2.1.00/01.0001 and CZ.1.05/1.1.00/02.0123), by the Czech Grant Agency (203/08/0114 and P503/12/0572), by the Grant Agency of the Czech Academy of Sciences (IAA401630901) and by the Brno Ph.D. Talent Scholarship – Funded by the Brno City Municipality. The access to computing facilities owned by parties and projects contributing to the MetaCentrum and listed at http://www.metacentrum.cz/acknowledgment/ is highly appreciated.

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