IL-4I1 Proteins and Enzymes

Interleukin 4 induced protein 1 (IL-4I1), also known as protein FIG-1 and L-amino acid oxidase, is encoded by a B-cell IL-4-inducible gene, FIG1, and is highly expressed in primary metastinal B-cell lymphomas. It belongs to the flavin monoamine oxidase family, FIG1 subfamily. Enzymological characterization reveals that IL-4I1 has L-amino acid oxidase activity with preference toward aromatic amino acids. Studies have shown that hIL-4I1 inhibited the proliferation of CD3-stimulated T lymphocytes with a similar effect on CD4(+) and CD8(+) T cells. Its inhibitory effect was dependent on enzymatic activity and H₂O₂ production. Its restricted expression to lymphoid tissues indicates that it may play an important function in the immune system.