Prolamin

prolamin [prō′lam·ən]

(biochemistry)

Any of the simple proteins, such as zein, found in plants; soluble in strong alcohol, insoluble in absolute alcohol and water.

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Prolamin 

a simple reserve protein found only in the seeds of cereals. Prolamins include gliadin, found in wheat and rye, zein, found in corn, hordein, found in barley, avenin, found in oats, oryzin, found in rice, and kaffirin, found in sorghum. Prolamins are soluble in 60–80 percent aqueous ethyl alcohol. They contain radicals of glutamic acid (over 40 percent) and proline (about 15 percent) but very little lysine, which accounts for the biological inferiority of the reserve proteins of grain crops.

Prolamins are heterogeneous. It is possible to divide them by means of chromatography and electrophoresis into components that are closely related in amino-acid composition but that differ in molecular weight and electrical charge; for example, the prolamin of wheat divides into 15 to 30 components with molecular weights that range from 31,000 to 78,000. The majority of components consist of a single polypeptide chain. Some components are capable of polymerizing through disulfide bonds and becoming parts of glutelins. The componential composition of gliadin is determined genetically and is an indicator of wheat variety. In wheat grains, gliadin and glutenin form gluten; the bread-baking quality of wheat depends on the content and physical properties of gluten.

A. B. VAKAR