Gluten is a class of proteins found many grains.
When most people refer to “gluten”, they usually mean the types found in the grains listed above.
The high-gluten content in wheat makes this grain unique. It is prized for how it affects the consistency of baked goods. It holds food together, yet before it is baked it is highly elastic. This combination allows bread to rise with a nice network of bubbles throughout, then become solid yet chewy when baked.
The bubbles in bread are formed by carbon dioxide which is produced by the yeast in bread. Yeast will ferment nicely in gluten-free flours, but it is the elastic nature gluten that allows yeast to raise the bread properly.
Gluten-free flours rely on a blend of fours, and often various types of gums to simulate the effects of gluten.
Gluten also provides the strength necessary to make thin pastry, that may be flaky, depending on the recipe,but not crumbly.
Gluten has the unfortunate affect on people with celiac disease of destroying their intestines, and eventually other internal organs.
Someone suffering from a gluten allergy is allergic to one or more types of gluten protein. It may be that they can be allergic to one type of gluten (e.g. wheat gluten) but not other types of gluten.
Gliadin allows bread to rise properly and maintain its shape while baking.
It is also the primary pathogen for people with celiac disease.
Gliadin is sometimes used as a delivery method for certain types of enzymes, such as superoxide dismutase, by fusing it to gliadin. This allows the enzyme to get past the stomach without breaking down in stomach acid.
Processed gliadin may be involved in causing a gluten allergy.
Avoiding wheat gets you 95% of the way towards avoiding gluten. See these links for more information about a wheat-free diet: