A comparative study of nitrilases identified by genome mining

Area of Science:

• Biochemistry
• Enzymology
• Microbiology

Background:

• Nitrilases are enzymes capable of transforming nitriles into valuable products.
• Understanding the substrate specificity of different nitrilases is crucial for industrial applications.
• Escherichia coli is a common host for expressing microbial enzymes.

Purpose of the Study:

• To characterize nitrilase enzymes from diverse microbial sources.
• To identify nitrilases with potential for industrial biotransformations.
• To evaluate the substrate scope of selected nitrilases.

Main Methods:

• Expression of various nitrilase genes in Escherichia coli.
• Enzymatic assays to determine substrate transformation capabilities.
• Substrate screening using different nitrile compounds and KCN.

Main Results:

• Six nitrilases were identified as arylacetonitrilases.
• Two enzymes functioned as cyanide hydratases.
• Several nitrilases demonstrated substrate preference for (hetero)aromatic nitriles.
• Rhodococcus ruber nitrilase showed high activity towards 3-cyanopyridine, 4-cyanopyridine, and bromoxynil.
• Neurospora crassa and Aspergillus niger nitrilases were effective for (R,S)-mandelonitrile.
• Aspergillus niger cyanide hydratase efficiently transformed KCN and 2-cyanopyridine.

Conclusions:

• Diverse nitrilases exhibit distinct substrate specificities.
• Specific nitrilases, such as from R. ruber, N. crassa, and A. niger, are promising candidates for industrial biotransformation of nitriles and KCN.
• This study provides valuable insights for enzyme discovery and engineering in nitrile bioconversion.