Gliadin is a glycoprotein present in wheat and several other cereals within the grass genus Triticum. Gliadins are prolamins and are separated on the basis of electrophoretic mobility and isoelectric focusing.
- α-/β-gliadins - soluble in low percentage alcohols.
- γ-gliadins - ancestral form of cysteine-rich gliadin with only intrachain disulfide bridges
- ω-gliadins - soluble in higher percentages, 30–50% acidic acetonitrile.
Gliadins are best known for their role, along with glutenin, in the formation of gluten. It is around 60% soluble in ethanol and contains only intramolecule disulfide links. These proteins are essential giving bread the ability to rise properly and fix shape on cooking. They are also some of the best examples of food-derived pathogenesis. People with gluten-sensitive enteropathy (the severe form of which is coeliac disease) are sensitive to α, β, and γ gliadins. Those with wheat-dependent (WD) exercise-induced anaphylaxis, WD urticaria and Baker's asthma are sensitive to ω-gliadins.
Gliadin can also serve as a useful delivery method for sensitive enzymes (such as superoxide dismutase, which is fused with gliadin to form glisodin) -- this helps protect them from stomach acids which cause breakdown.
For useful description of the gliadins see:
Deamidated gliadin is produced by acid or enzymatic treatment of gluten. The enzyme, tissue transglutaminase, converts some of the abundant glutamines to glutamic acid. This is done because gliadins are soluble in alcohol and cannot be mixed with other foods (like milk) without changing the foods qualities. Deamidated gliadin is soluble in water. The cellular immunity to deamidated α-/β-gliadin is much greater than α/β-gliadin and can result in symptomatic gluten-sensitive enteropathy.