Nitrile Reductase from <i>Geobacillus kaustophilus</i>: A Potential Catalyst for a New Nitrile Biotransformation Reaction

Abstract

Abstract The cloning, expression and characterization of a nitrile reductase (NRed) from the thermophile Geobacillus kaustophilus is reported. The enzyme shows a 12‐fold increase in activity in response to a temperature change from 25 °C to 65 °C. The substrate scope regarding its biocatalytic applicability was investigated by testing a range of common nitriles. The narrow substrate range observed for the wild‐type enzyme prompted the rational design of Gk NRed active site mutants based on a previously published homology model from Bacillus subtilis . The activities of the mutants and the wild‐type enzyme were investigated in their structure‐function relationship regarding the natural substrate 7‐cyano‐7‐deazaguanine (preQ 0 ) as well as a range of synthesized preQ 0 ‐like substrate structures. A distinct dependence of the wild‐type enzyme activity on specific structural modifications of the natural substrate was observed. Two non‐natural nitriles derived from preQ 0 could be reduced to their corresponding amino compounds.