Chlorine kinetic isotope effects on the haloalkane dehalogenase reaction

We have found chlorine kinetic isotope effects on the dehalogenation catalyzed by haloalkane dehalogenase from Xanthobacter autotrophicus GJ10 to be 1.0045 ± 0.0004 for 1,2-dichloroethane and 1.0066 ± 0.0004 for 1-chlorobutane. The latter isotope effect approaches the intrinsic chlorine kinetic isotope effect for the dehalogenation step. The intrinsic isotope effect has been modeled using semiempirical and DFT theory levels using the ONIOM QM/QM scheme. Our results indicate that the dehalogenation step is reversible; the overall irreversibility of the enzyme-catalyzed reaction is brought about by a step following the dehalogenation.
Addresses: Paneth P, Lodz Tech Univ, Dept Chem, Zeromskiego 116, PL-90924 Lodz, Poland. Lodz Tech Univ, Dept Chem, PL-90924 Lodz, Poland. Univ Uppsala, Ctr Biomed, Dept Biochem, S-75123 Uppsala, Sweden. Univ Uppsala, Dept Chem, S-75121 Uppsala, Sweden.