Classification|Simple|Proteins|Biochemistry|Pharmacy Technician|Dr Muhammad Naeem Asghar Pharmacist

Описание: Classification|Simple|Proteins|Biochemistry|Pharmacy Technician|Dr Muhammad Naeem Asghar Pharmacist
‪@drnaeempharmacist381‬
CLASSIFICATION OF PROTEINS
Proteins have been classified in several ways. The following classification is
based upon physicochemical properties of proteins.
A protein may belong to one of the three types, i.e.
I.
Simple proteins.
II.
Compound or conjugated proteins.
III. Derived proteins.
SIMPLE PROTEINS
On hydrolysis, these proteins yield only amino acids or their derivatives.
These consist of the following types.
1. Albumins:
These are water-soluble proteins and occur in both plant and animal
kingdoms.
Examples are serum albumin, ovalbumin and lactalbumin m animals and
legume in plants.
2. Globulins:
These are insoluble in water but soluble in dilute salt solutions and are heatcoagulable to a variable extent.
They are found in animals,
e.g. lactoglobulin, myosin in muscle, ovoglobulin, serum globulins and also
in plants, e.g. legumin.
Globins
These are rich in histidine but are not basic. They unite with heme to form
hemoglobin.
Hemoglobin of different species differs only with respect to globin, but the
heme part is the same in all cases.
4. Prolamins
These are soluble in 70 to 80% ethanol but are insoluble in water and
absolute alcohol. Examples are gliadin of wheat and zein of maize. These
are rich in the amino acid proline but deficient in lysine.
5. Histones
These are very strongly basic proteins as they are rich in arginine. In
combination with deoxyribonucleic acid (DNA) they form nucleoproteins
(nucleohistones). The association of DNA and histones gives rise to
complexes called nucleosomes.
6. Protamines
These are present in sperm cells like histones; they form nucleoproteins
with nucleic acids and are rich in arginine. These proteins lack in both
tyrosine and tryptophan.
7. Albuminoids
These are also called scleroproteins [sclero = hard] and occur only in
animals; they do not occur in plants. These proteins includes
i) Collagen
ii) Elastin
iii) Keratin