This gene encodes a secreted L-amino acid oxidase protein which primarily catabolizes L-phenylalanine and, to a lesser extent, L-arginine. The expression of this gene is induced by the cytokine interleukin 4 in B cells. This gene is also expressed in macrophages and dendritic cells. This protein may play a role immune system escape as it is expressed in tumor-associated macrophages and suppresses T-cell responses. This protein also contains domains thought to be involved in the binding of flavin adenine dinucleotide (FAD) cofactor. Multiple transcript variants encoding different isoforms have been found for this gene. Some transcripts of this gene share a promoter and exons of the 5' UTR with the overlapping NUP62 gene. [provided by RefSeq, Jul 2020]