title: Important amino acid residues of hexachlorocyclohexane dehydrochlorinases (LinA) for enantioselective transformation of hexachlorocyclohexane isomers.
abstract: LinA-type1 and LinA-type2 are two well-characterized variants of the enzyme 'hexachlorocyclohexane (HCH)-dehydrochlorinase'. They differ from each other at ten amino acid positions and exhibit differing enantioselectivity for the transformation of the (-) and (+) enantiomers of α-HCH. Amino acids responsible for this enantioselectivity, however, are not known. An in silico docking analysis identified four amino acids (K20, L96, A131, and T133) in LinA-type1 that could be involved in selective binding of the substrates. Experimental studies with constructed mutant enzymes revealed that a combined presence of three amino acid changes in LinA-type1, i.e. K20Q, L96C, and A131G, caused a reversal in its preference from the (-) to the (+) enantiomer of α-HCH. This preference was enhanced by the additional amino acid change T133 M. Presence of these four changes also caused the reversal of enantioselectivity of LinA-type1 for δ-HCH, and β-, γ-, and δ-pentachlorocyclohexens. Thus, the residues K20, L96, A131, and T133 in LinA-type1 and the residues Q20, C96, G131, and M133 in LinA-type 2 appear to be important determinants for the enantioselectivity of LinA enzymes.
authors.affiliation: Academy of Scientific and Innovative Research, New Delhi, India.|Environmental Biotechnology Section, CSIR-Indian Institute of Toxicology Research, Lucknow, India.
authors.forename: Nidhi
authors.initials: N
authors.lastname: Shrivastava
authors.affiliation: Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
authors.forename: Ankit S
authors.initials: AS
authors.lastname: Macwan
authors.affiliation: Department of Environmental Microbiology, Swiss Federal Institute for Aquatic Science and Technology (Eawag), Dübendorf, Switzerland. hanspeter.kohler@eawag.ch.
authors.forename: Hans-Peter E
authors.identifier: 0000-0001-7667-0762
authors.initials: HE
authors.lastname: Kohler
authors.affiliation: Academy of Scientific and Innovative Research, New Delhi, India.|Environmental Biotechnology Section, CSIR-Indian Institute of Toxicology Research, Lucknow, India.
authors.forename: Ashwani
authors.initials: A
authors.lastname: Kumar
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D001673:Biodegradation, Environmental; D002849:Chromatography, Gas; D001556:Hexachlorocyclohexane / Q000737:chemistry* / Q000378:metabolism*; D008190:Lyases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D000596:Amino Acids; D050505:Mutant Proteins; C040534:alpha-hexachlorocyclohexane; C086916:delta-hexachlorocyclohexane; D001556:Hexachlorocyclohexane; D008190:Lyases; C019994:dehydrochlorinases
keywords: Enantioselectivity; HCH dehydrochlorinase LinA; α-HCH enantiomers