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 Vmax and Km 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. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)