Multi-functional transglutaminase 2 (TG2), which possesses protein cross-linking and GTP hydrolysis activities, is involved in various cellular processes, including apoptosis, angiogenesis, wound healing, and neuronal regeneration, and is associated with many human diseases, including inflammatory disease, celiac disease, neurodegenerative disease, diabetes, tissue fibrosis, and cancers. The gene discussed is TGM2; the disease is diabetes mellitus.