Cyclohexylamine oxidase as a useful biocatalyst for the kinetic resolution and dereacemization of amines

The biocatalytic performance of a cloned cyclohexylamine oxidase derived from Brevibacterium oxydans IH-35A towards structurally different amines was investigated. Cycloalkyl primary amines, alkyl aryl amines, and α-carbon-substituted aliphatic amines were identified as suitable substrates for the biocatalyst based on an activity assay. Kinetic resolutions of several amines by either recombinant whole cells or crude enzyme extracts prepared therefrom gave enantiomerically pure (R)-amines besides the corresponding ketones. When cyclohexylamine oxidase in combination with a borane–ammonia complex as reducing agent was applied to the deracemization of several substrates, excellent enantiomeric ratios (>99:1) and good isolated yields (62%–75%) of the corresponding (R)-amines were obtained.