Purification and properties of alpha-amino-epsilon-caprolactam racemase from Achromobacter obae

We have purified a unique enzyme, alpha-amino-epsilon-caprolactam racemase 945-fold from an extract of Achromobacter obae by Octyl-Sepharose CL-4B and Thiopropyl-Sepharose 6B and some other chromatographies. The purified enzyme was found homogeneous by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and analytical ultracentrifugation. The enzyme has a monomeric structure with Mr approximately 50000 and a sedimentation coefficient (S20,w) of 4.28 S. The enzyme contains pyridoxal 5'-phosphate as a coenzyme. The pH optimum for the enzyme activity is approximately 9.0. D- and L-alpha-amino-epsilon-caprolactams are the only substrates. The Km values for the D- and L-isomers are, 8 and 6 mM, respectively.