Bacterial assimilation of d- and l-2-chloropropionates and occurrence of a new dehalogenase

The occurrence of a new bacterial dehalogenase acting on both the optical isomers of 2-halogenated alkanoic acids was demonstrated. When the haloalkanoic acid-utilizing bacteria were screened in a medium containing dl-2-chloropropionate as a sole carbon source, two types of bacteria were isolated: (1) a few strains utilizing both d- and l-isomers of 2-chloropropionate and (2) strains utilizing only the l-isomer. A dehalogenating enzyme was obtained from the cells of Pseudomonas sp. which is able to utilize both isomers. The crude enzyme catalyzed the dehalogenation of d- and l-2-chloropropionates to yield l- and d-isomers of lactate, respectively. The enzyme showed the same pH optimum and heat inactivation rate for the d- and l-isomers. Apparent K_m values for d- and l-2-chloropropionates were 4.5 and 1.0 mM, respectively. The enzyme acted specifically on 2-haloalkanoic acids. Activity staining of disc-gels electrophoresed witg the crude enzyme preparation showed that the dehalogenation of d- and l-2-chloropropionates, monochloroacetate, dichloroacetate, 2,2-dichloropropionate, and dl-2-chlorobutyrate is due to a single protein.Abbreviations MCA monochloroacetic acid - DCA dichloroacetic acid - TCA trichloroacetic acid - 2 MCPA 2-monochloropropionic acid - 22 DCPA 2,2-dichloropropionic acid - 3 MCPA 3-monochloropropionic acid - 2 MCBA 2-monochlorobutyric acid - 3 MCBA 3-monochlorobutyric acid - 4 MCBA 4-monochlorobutyric acid