Title: Stereochemistry of LinB-catalyzed biotransformation of δ-HBCD to 1R,2R,5S,6R,9R,10S-pentabromocyclododecanol
Authors : Heeb, Norbert V.
Zindel, Daniel
Graf, Heidi
Azara, Valeria
Bernd Schweizer, W.
Geueke, Birgit
Kohler, Hans-Peter E.
Lienemann, Peter
Published in : Chemosphere
Volume(Issue) : 90
Issue : 6
Pages : 1911
Pages to: 1919
Publisher / Ed. Institution : Elsevier
Issue Date: 2013
License (according to publishing contract) : Licence according to publishing contract
Type of review: Peer review (publication)
Language : English
Subjects : Catalysis; Brominated hydrocarbons; Nucleotidyltransferases; Soil Pollutants; Sphingomonadaceae; Stereoisomerism; Biotransformation
Subject (DDC) : 572: Biochemistry
Abstract: The haloalkane dehalogenase LinB from Sphingobium indicum B90A converts β-hexachlorocyclohexane (β-HCH), the most persistent HCH stereoisomer, to mono- and dihydroxylated metabolites. Recently, we reported that LinB also transforms α-, β- and γ-hexabromocyclododecanes (HBCDs), which are structurally related to HCHs. Here, we show that LinB catalyzes the hydroxylation of δ-HBCD to two pentabromocyclododecanols (PBCDOHs) and two tetrabromocyclododecadiols (TBCDDOHs). The stereochemistry of this enzymatic transformation was deduced from XRD crystal structure data of the substrate δ-HBCD and α(2)-PBCDOH, one of the biotransformation products. Five stereocenters of δ-HBCD are unchanged but the one at C6 is converted to an alcohol with inversion from S- to R-configuration in a nucleophilic, S(N)2-like substitution reaction. Only α(2)-PBCDOH with the 1R,2R,5S,6R,9R,10S-configuration is obtained but not its enantiomer. With only two of the 64 PBCDOHs formed, these transformations indeed are regio- and stereoselective. A conformational analysis revealed that the triple-turn motive, which is predominant in δ-HBCD and in several other HBCD stereoisomers, is also found in the product. This shows that LinB preferentially converted reactive bromine atoms but not those in the conserved triple-turn motive. The widespread contamination with HCHs triggered the bacterial evolution of dehalogenases which acquired the ability to convert these pollutants and their metabolites. We here demonstrate that LinB of S. indicum also transforms HBCDs regio- and stereoselectively following a similar mechanism.
Departement: Life Sciences and Facility Management
Organisational Unit: Institute of Chemistry and Biotechnology (ICBT)
Publication type: Article in scientific journal
DOI : 10.1016/j.chemosphere.2012.10.019
ISSN: 0045-6535
1879-1298
URI: https://digitalcollection.zhaw.ch/handle/11475/12903
Appears in Collections:Publikationen Life Sciences und Facility Management

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