Kinetic and sequence-structure-function analysis of known LinA variants with different hexachlorocyclohexane isomers

Background

Here we report specific activities of all seven naturally occurring LinA variants towards three different isomers, α, γ and δ, of a priority persistent pollutant, hexachlorocyclohexane (HCH). Sequence-structure-function differences contributing to the differences in their stereospecificity for α-, γ-, and δ-HCH and enantiospecificity for (+)- and (?)-α -HCH are also discussed.

Methodology/Principal Findings

Enzyme kinetic studies were performed with purified LinA variants. Models of LinA2_B90A A110T, A111C, A110T/A111C and LinA1_B90A were constructed using the FoldX computer algorithm. Turnover rates (min^?1) showed that the LinAs exhibited differential substrate affinity amongst the four HCH isomers tested. α-HCH was found to be the most preferred substrate by all LinA''s, followed by the γ and then δ isomer.

Conclusions/Significance

The kinetic observations suggest that LinA-γ1-7 is the best variant for developing an enzyme-based bioremediation technology for HCH. The majority of the sequence variation in the various linA genes that have been isolated is not neutral, but alters the enantio- and stereoselectivity of the encoded proteins.