Overexpression and characterisation of non-stereospecific haloacid Dehalogenase E (DehE) of Rhizobium sp.

The Rhizobium sp. dehalogenase enzyme (DehE) produced by heterologous expression of the cloned gene in E.coli was purified and characterised. The K m , K cat and the Specificity Constants were determined. The enzyme shows non- stereospecific and could act on D- and L- isomer of 2-chloropropionate. The derived amino acid sequence of DehE showed little identity to Pseudomonas putida 113 DL-DEX (39% homology) but there was significant identity to two other dehalogenases (DehI and DhlIV) - 72% homology, that act non-selectively on 2-chloropropionate. The amino acid sequence of dehE contains 4 cysteine residues but their involvement in the mechanism of catalysis is still unclear based on their end product configuration. The K m , K cat and Specificity Constants values for brominated compound suggested that this compound is a better substrate for growth and for the DehE enzyme.