Human Nutrition 3(3+0)

Lesson 16 : Proteins

Simple proteins

Proteins which yield only amino acids or their derivatives on hydrolysis.

1. Albumins: Soluble in pure water and coagulable by heat.
   Ex: egg albumin, serum albumin (blood)

2. Globulins: Insoluble in pure water, but soluble in neutral salt solutions.
   Ex : serum globulin (blood), tuberin (potato), arachin and conarachin (groundnut).

3. Glutelins: Insoluble in all neutral solvents, but soluble in very dilute acids and alkalis. The best known protein of this group is the glutenin of wheat.

4. Prolamins: Soluble in 70-80 per cent alcohol.
   Ex : gliadin (wheat) and zein (maize)

5. Fibrous proteins: Proteins characteristic of the skeletal structures of animals and also of the external protective tissues, such as skin, hair, etc.
   Ex : collagen, elastin and keratin.

6. Histones: Soluble in water and insoluble in very dilute ammonia. On hydrolysis they yield several amino acids, among which the basic ones predominate. The important members of this group are the thymus histones and the globin of haemoglobin.

7. Protamins: Strongly basic proteins of low molecular weight, soluble in water, not coagulable by heat and on hydrolysis which yield large amounts of basic amino acids.
   Ex : Salmine from salmon sperm.