Identification and development of amino acid oxidases

Amino acid oxidases are an important class of enzymes that mostly participate in the oxidation of amino acids using FAD as a cofactor. Many of them function in the catabolism of amino acids with wider substrate specificities. On the other hand, based on the recent, successful use of the enzymes for diagnoses with new cofactor and mechanism, highly selective enzymes have been screened from Nature, and many new enzymes have been discovered and further characterized by X-ray crystallography. As a result of the screening for amino acid oxidases with biosynthetic or antibiotic functions, l-Trp oxidase, l-Lys oxidases, and Gly oxidase have been found. The pyridoxal phosphate-dependent l-Arg oxidase has the intriguing new activity of hydroxylating unactivated CC bonds. A new amine oxidase was created by the protein engineering of d-amino acid oxidase. Recent developments in the characterization of amino acid oxidases and their applications are summarized.