218
• Globular or Corpuscular proteins (e.g. Cytochrome C, Blood proteins,
Enzymes, nutrient proteins)
• Fibrous or Fibrillar proteins and they can be further classified as collagen,
elastin, keratin and fibrion
c. Classification based on composition and solubility
• Simple proteins or holoproteins, they can be further classified mainly on the
basis of their solubility like protamines and histones, albumins, globulins,
glutelins, prolamines, scleroproteins and albuminoids.
• Conjugated or complex proteins or heteroproteins can be further classified
based on the nature of the prosthetic group present. The various divisions are
metalloproteins, chromoproteins, glycoproteins, phosphoproteins, lipoproteins and nucleoproteins. (Instead of metalloproteins, chromoproteins etc.,
the terms metalloproteids, chromoproteids etc., are sometimes used.)
• Derived proteins which are derivatives of proteins resulting from the action of
heat, enzymes or chemical agents. They are further classified as primary
derived proteins and secondary derived proteins. Primary derived proteins
include proteans, metaproteans or infra proteins and coagulated proteins.
Secondary derived proteins include proteoses, peptones and polypeptides.
d. Classification based on biological function
• Depending upon their physical and chemical structure and location inside the
cell, different proteins perform various functions. Because of their diverse
nature proteins may be catgorised under following groups which is based on
the metabolic functions they perform and include enzymatic proteins, structural proteins, transport or carrier proteins, nutrient and storage proteins, contractile or motile proteins, defense proteins, regulatory proteins and toxic
proteins.
In addition to this Osborne (1924) classified proteins into four groups on the
basis of their extraction and solubility in water (albumins), dilute saline (globulins),
alcohol hater mixtures (prolamins), and dilute acid or alkali (glutelins). The major
seed storage proteins include albumins, globulins, and prolamins. According to this
definition, albumins are soluble in water, but globulins are insoluble in water and
soluble in dilute salt solutions. Prolamins are alcohol soluble and glutelins are alkali
soluble proteins. Albumins and globulins are referred as soluble proteins (Salunkhe
et al. 1992). The general classification of proteins is shown in Fig. 4.
Main Storage Proteins of Cereals
It is important to pay attention towards the nature of protein before employing them
in any process. Usually they fall into two classes: the prolamins, which are present
in cereals and a predominance of globulins with some albumins in pseudo-cereals
N. A. Mir et al.
• Globular or Corpuscular proteins (e.g. Cytochrome C, Blood proteins,
Enzymes, nutrient proteins)
• Fibrous or Fibrillar proteins and they can be further classified as collagen,
elastin, keratin and fibrion
c. Classification based on composition and solubility
• Simple proteins or holoproteins, they can be further classified mainly on the
basis of their solubility like protamines and histones, albumins, globulins,
glutelins, prolamines, scleroproteins and albuminoids.
• Conjugated or complex proteins or heteroproteins can be further classified
based on the nature of the prosthetic group present. The various divisions are
metalloproteins, chromoproteins, glycoproteins, phosphoproteins, lipoproteins and nucleoproteins. (Instead of metalloproteins, chromoproteins etc.,
the terms metalloproteids, chromoproteids etc., are sometimes used.)
• Derived proteins which are derivatives of proteins resulting from the action of
heat, enzymes or chemical agents. They are further classified as primary
derived proteins and secondary derived proteins. Primary derived proteins
include proteans, metaproteans or infra proteins and coagulated proteins.
Secondary derived proteins include proteoses, peptones and polypeptides.
d. Classification based on biological function
• Depending upon their physical and chemical structure and location inside the
cell, different proteins perform various functions. Because of their diverse
nature proteins may be catgorised under following groups which is based on
the metabolic functions they perform and include enzymatic proteins, structural proteins, transport or carrier proteins, nutrient and storage proteins, contractile or motile proteins, defense proteins, regulatory proteins and toxic
proteins.
In addition to this Osborne (1924) classified proteins into four groups on the
basis of their extraction and solubility in water (albumins), dilute saline (globulins),
alcohol hater mixtures (prolamins), and dilute acid or alkali (glutelins). The major
seed storage proteins include albumins, globulins, and prolamins. According to this
definition, albumins are soluble in water, but globulins are insoluble in water and
soluble in dilute salt solutions. Prolamins are alcohol soluble and glutelins are alkali
soluble proteins. Albumins and globulins are referred as soluble proteins (Salunkhe
et al. 1992). The general classification of proteins is shown in Fig. 4.
Main Storage Proteins of Cereals
It is important to pay attention towards the nature of protein before employing them
in any process. Usually they fall into two classes: the prolamins, which are present
in cereals and a predominance of globulins with some albumins in pseudo-cereals
N. A. Mir et al.