Monitoring of in vitro deamidation of gliadin peptic fragment by mass spectrometry may reflect one of the molecular mechanisms taking place in celiac disease development.

Celiac disease, a chronic disorder of the small intestine, is caused by dietary gluten and is characterized by villous atrophy and local inflammation associated with infiltration of B and T lymphocytes and/or macrophages into the intestinal wall. In genetically predisposed individuals, the infiltrating cells are activated by gluten, gliadin and their proteolytic fragments and produce chemokines, cytokines and reactive radicals. The sequence of one of the macrophage-stimulatory gliadin peptic fragment was determined by mass spectrometry (MS) as VSFQQPQQQYPSSQ. The role of tissue transglutaminase (tTG) in innate immunity stimulation was studied by mass spectrometric monitoring of sequence changes in this active peptide. Two sites of glutamine deamidation in this peptide were localized by high-resolution scanning in MS/MS mode in an ion trap. A single deamidation in the parent peptide led to the complete loss of its stimulatory effect on macrophages.