A single point mutation enhances hydroxynitrile synthesis by halohydrin dehalogenase.
Article Details
- CitationCopy to clipboard
Schallmey M, Jekel P, Tang L, Majeric Elenkov M, Hoffken HW, Hauer B, Janssen DB
A single point mutation enhances hydroxynitrile synthesis by halohydrin dehalogenase.
Enzyme Microb Technol. 2015 Mar;70:50-7. doi: 10.1016/j.enzmictec.2014.12.009. Epub 2014 Dec 24.
- PubMed ID
- 25659632 [ View in PubMed]
- Abstract
The cyanide-mediated ring opening of epoxides catalyzed by halohydrin dehalogenases yields beta-hydroxynitriles that are of high interest for synthetic chemistry. The best studied halohydrin dehalogenase to date is the enzyme from Agrobacterium radiobacter, but this enzyme (HheC) exhibits only low cyanolysis activities. Sequence comparison between a pair of related halohydrin dehalogenases from Corynebacterium and Mycobacterium suggested that substitution of a threonine that interacts with the active site might be responsible for the higher cyanolytic activity of the former enzyme. Here we report that a variant of HheC in which this substitution (T134A) is adopted displays an up to 11-fold higher activity in cyanide-mediated epoxide ring-opening. The mutation causes removal of the hydrogen bond between residue 134 and the side chain O of the active site serine 132, which donates a hydrogen bond to the substrate oxygen. The mutation also increases dehalogenase rates with various substrates. Structural analysis revealed that the anion-binding site of the mutant enzyme remained unaltered, showing that the enhanced activity is due to altered interactions with the substrate oxygen rather than changes in the nucleophile binding site.