HALOALKANOATE DEHALOGENASE-II (DEHE) OF A RHIZOBIUM SP. - MOLECULAR ANALYSIS OF THE GENE AND FORMATION OF CARBON-MONOXIDE FROM TRIHALOACETATE BY THE ENZYME

A 3-kb EcoRI fragment of genomic DNA from a Rhizobium sp. cloned into pUC19 endowed Escherichia coli K-12 with the ability to grow, albeit s lowly, with 2-chloropropionic acid as substrate. The construct express ed weakly a gene that encoded a non-stereospecific 2-chloropropionic a cid dehalogenase (dehalogenase II; DehE). The dehE gene was not closel y linked to the organism's other two dehalogenase genes, dehD and dehL . The derived amino acid sequence of DehE showed little identity with DehD or DehL, but there was significant identity to two other dehaloge nases that act non-selectively on 2-chloropropionic acid. The fragment carried a truncated ORF upstream of dehE that was 51% identical to a positively acting regulatory protein, DehR, required for expression of a Pseudomonas putida dehalogenase gene. In its complete form this gen e could encode the Rhizobium sp. dehalogenase-regulatory protein. DehE dehalogenated tribromoacetic acid completely, forming stoichiometric amounts of carbon monoxide and carbon dioxide as the other products.