research papers
The crystal structure of the novel haloalkane dehalogenase DbeA from Bradyrhizobium elkanii USDA94 revealed the presence of two chloride ions buried in the protein interior. The first halide-binding site is involved in substrate binding and is present in all structurally characterized haloalkane dehalogenases. The second halide-binding site is unique to DbeA. To elucidate the role of the second halide-binding site in enzyme functionality, a two-point mutant lacking this site was constructed and characterized. These substitutions resulted in a shift in the substrate-specificity class and were accompanied by a decrease in enzyme activity, stability and the elimination of substrate inhibition. The changes in enzyme catalytic activity were attributed to deceleration of the rate-limiting hydrolytic step mediated by the lower basicity of the catalytic histidine.
Keywords: haloalkane dehalogenase; halide-binding site; catalytic activity; substrate specificity; enzyme stability.
Supporting information
Portable Document Format (PDF) file https://doi.org/10.1107/S1399004714009018/dw5094sup1.pdf |
PDB reference: DbeA, 4k2a