The crystal structure of the nitrile hydratase (NHase) from Bacillus smithii
SC-J05-1 was determined. Our analysis of the structure shows that some residues
that seem to be responsible for substrate recognition are different from those
of other NHases. In particular, the Phe52 in the beta subunit of NHase from B.
smithii covers the metal center partially like a small lid and narrows the
active site cleft. It is well known that the NHase from B. smithii especially
prefers aliphatic nitriles for its substrate rather than aromatic ones, and we
can now infer that the Phe52 residue may play a key role in the substrate
specificity for this enzyme. This finding leads us to suggest that substitution
of these residues may alter the substrate specificity of the enzyme.
