Biosynthesis of α-keto acids and resolution of chiral amino acids by l-amino acid deaminases from Proteus mirabilis

Chiral amino acids and their deamination products, α-keto acids, have important applications in food, medicine, and fine chemicals. In this study, two l -amino acid deaminase genes from Proteus mirabilis , PM473 of type Ⅰ and PM471 of type Ⅱ were cloned and expressed in Escherichia coli respectively, expected to achieve the chiral separation of amino acids . Extensive substrate preference testing showed that both deaminases had catalytic effects on the d -amino acid component of the D, l -amino acids, and PM473 has a wider catalytic range for amino acids. When D, L-Cys was used as the substrate, all L-Cys components and 75.1 % of D-Cys were converted to mercapto pyruvate , and the remaining D-Cys was a single chiral enantiomer . Molecular docking analysis showed that the interaction between the substrate and the key residues affected the stereoselectivity of enzymes . The compatibility of hydrophobicity between the binding pocket and substrate may be the basic factor that affects the substrate selectivity. This work provides an alternative method for the production of α-keto acids and the resolution of chiral amino acids.