BACTERIAL 2-HALOACID DEHALOGENASES - STRUCTURES AND CATALYTIC PROPERTIES

2-Haloacid dehalogenases (2-haloacid halidohydrolase; EC class: 3.8.1. 2) catalyze the hydrolytic dehalogenation of 2-haloalkanoic acids to p roduce the corresponding 2-hydroxyalkanoic acids. Four different group s of 2-haloacid dehalogenases have been found in bacterial cells. The carboxylate group of Asp(10) of L-2-haloacid dehalogenase acts as a nu cleophile on the alpha-carbon of L-2-haloalkanoic acid to form an este r intermediate, which is hydrolyzed to produce the corresponding 2-hyd roxyalkanoic acid. In contrast, in the reaction of DL-2-haloacid dehal ogenase (inversion type), a water molecule activated by the enzyme dir ectly attacks the alpha-carbon of the substrate. D-2-Haloacid dehaloge nase shows sequence similarity to DL-2-haloacid dehalogenase (inversio n type), suggesting that the reaction mechanism of D-2-haloacid dehalo genase is similar to that of DL-2-haloacid dehalogenase (inversion typ e). Only the DL-2-haloacid dehalogenase (retention type) reaction proc eeds with retention of the C-2-configuration of the substrate, and its reaction mechanism is probably different from those of other 2-haloac id dehalogenases.