[The involvement of transglutaminase 2 in autoimmunological diseases]

Transglutaminase 2 (TG-ase 2) is one of the enzymes which catalyzes the deamination and transacylation of proteins. The transfer of a glutamine acyl residue to a lysine amine group of the acceptor protein is one of the posttranslational covalent modifications regulating some polypeptide activities. The control of protein oligomerization by TG-ase 2 is a cause of the formation of detergent-insoluble macromolecular aggregates. These inclusions are present in degenerating cells during, for example, Alzheimer's and Parkinson's disease. Overexpression of TG-ase 2 has been noted in apoptotic cells. Protein reserves in cereals are rich in glutamine, a substrate of TG-ase 2. Deamination of glutamine is the most important reaction for the initiation of the inflammatory process during gluten-dependent disease of the gut (celiac disease). Grains that contain gliadin are a cause of inflammatory reaction in children with intolerance to glutene. Interactions of the TG-ase product-glutamate with antigens of the major histocompatibility complex type II (MHC II, or HLA DQ) cause autoimmunological reaction by CD4+ T lymphocytes. Knowledge of the kinetic and molecular character of TG-ase 2 has contributed to finding peptides to replace gliadin. These molecules do not evoke immunological events.