Expression and characterization of a second L-amino acid deaminase isolated from Proteus mirabilis in Escherichia coli

L-amino acid deaminases catalyze the deamination of natural L-amino acids. Two types of L-amino acid deaminase have been identified in Proteus species. One exhibits high levels of activity toward a wide range of aliphatic and aromatic L-amino acids, typically L-phenylalanine, whereas the other acts on a relatively narrow range of basic L-amino acids, typically L-histidine. In this study, we cloned, expressed, and characterized a second amino acid deaminase, termed Pm1, from P. mirabilis KCTC 2566. Homology alignment of the deduced amino acid sequence of Pm1 demonstrated that the greatest similarity (96%) was with the L-amino acid deaminase (LAD) of P. vulgaris, and that homology with Pma was relatively low (72%). Also, similar to LAD, Pm1 was most active on L-histidine, indicating that Pm1 belongs to the second type of amino acid deaminase. In agreement with this conclusion, the V_max and K_m values of Pm1 were 119.7 (μg phenylpyruvic acid/mg/min) and 31.55 mM phenylalanine, respectively, values lower than those of Pma. The Pml deaminase will be very useful industrially in the preparation of commercially valuable materials including urocanic acid and α -oxoglutarate.