Storage proteins of endosperm and embryo

Storage proteins of endosperm and embryo,

STORAGE PROTEINS

Seed contains stored proteins in the form of definite bodies, protein bodies, protein granules or aleuron grains, or matrix proteins. These proteins can be distinguished from the metabolically active proteins by their disappearance during germination.

Protein bodies – are storage proteins that are located in cotyledons and endosperm.

Aleuron grains - are storage proteins that are located in the aleuron layer.

         

Usually, the storage proteins of seeds contain large amount of amide nitrogen that are formed by incorporation of aspargine and glutamine into the protein during synthesis. The storage proteins in seeds of dicotyledonous plants are present in the form of globulin e.g. in pulses with some amounts of glutellin and prolamine.  The ratio of these proteins is variable according to the species. In dicotyledonous plants endosperms and the cotyledons serve as storage organs.

      

In the monocotyledonous plants the primary storage organs is the endosperm which isin close contact with the embryo proper. Seeds of cereals generally contain relatively high concentrations of pralamines and gluteins with much lower concentrations o globulins. The scutellum also serves as a storage organ.

 Some important proteins:-

·         Zein – in corn zein (a Promlamine), is a major storage protein found in endosperm and contains a relatively large amount of alanine and leucine with little lysine and almost no tryptophane.

·         Glutein  - It is the major storage protein of wheat. It has elastic property necessary for making of bread and chapati.

·         Gliadin – It is other major class of proteins of wheat which does not have the elastic properties like glutein.