![]() ![]() However, if WWTP communities were sufficiently biodiverse to nearly saturate the set of possible positive effects, then positive associations would not occur between biodiversity and the rates of particular ecosystem functions. Theoretical considerations predict that WWTP communities with more biodiversity are more likely to contain strains that have positive effects on the rates of particular ecosystem functions, thus resulting in positive associations between those two variables. Whether differences in biodiversity translate into differences in the provision of particular ecosystem services, however, is under active debate. Configurations of both PBCDE metabolites were predicted by molecular docking experiments and confirmed in one case by XRD data.īiodiversities can differ substantially among different wastewater treatment plant (WWTP) communities. In conclusion, LinA2, a bacterial enzyme of the HCH-degrading strain Sphingobium indicum B90A was able to stereoselectively convert β-HBCDs. Both modeled enzyme-substrate complexes are in line with 1,2-diaxial HBr eliminations. The enzyme-substrate complex obtained from LinA2 and an activated conformation of (+)β-HBCD allows the HBr elimination at C9 and C10 leading to the predicted product. We predicted its stereochemistry to be 1 E,5 R,6 R,9 S,10 R-PBCDE from docking experiments. A second PBCDE of yet unknown configuration was obtained from (+)β-HBCD. A reasonable enzyme-substrate complex with the catalytic dyad His-73 and Asp-25 approaching the hydrogen at C6 and a cationic pocket of Lys-20, Try-42 and Arg-129 binding the leaving bromine at C5 was found from in silico docking experiments. Formation of this product can be rationalized by HBr elimination at C5 and C6. Here, we present the XRD crystal structure of 1 E,5 S,6 S,9 R,10 S-pentabromocyclododecene (PBCDE) and demonstrate that its enantiomer with the 1 E,5 R,6 R,9 S,10 R-configuration is the only metabolite formed during LinA2-catalyzed dehydrobromination of (-)β-HBCD. The transformation of (-)β-HBCD is considerably faster than that of its enantiomer. LinA2 selectively catalyzes the transformation of β-HBCDs other stereoisomers like α-, γ-, and δ-HBCDs are not converted. Both classes of compounds are persistent organic pollutants now regulated under the Stockholm Convention. ![]() LinA2, a bacterial enzyme expressed in various Sphingomonadaceae, catalyzes the elimination of HCl from hexachlorocyclohexanes (HCHs) and, as discussed here, the release of HBr from certain hexabromocyclododecanes (HBCDs). ![]()
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