The only proteins of the body that
are readily available for study in the human are those of the plasma. Although these, of course, represent
but a small fraction of the total protein content of the body, they form an
important group for both the pathologist and the clinician since their
measurement provides a useful diagnostic aid (Nelson et al, 2000).
The plasma proteins have been classified
in various ways. One approach has been to describe each protein in terms of its
physicochemical properties. Alternatively, a plasma protein can be described in
terms of its known function. Because the
total protein represents the sum of Albumin and globulin, it is important to
know which protein fraction is high or low.
SEPERATION OF PLASMA PROTIENS ON THE
BASIS OF PHYSICOCHEMICAL PROPERTIES includes
Albumin 40 - 57 g/l
Globulin 13 – 30 g/l
Fibrinogen 1 – 5 g/l
Total 62 – 82 g/l.
ALBUMIN
Albumin is the principal protein
synthesized by the liver using dietary protein and is passed directly into the
blood stream. Its function in the liver is to create an osmotic force that
maintains fluid volume in plasma because of its low MW (Nelson et al, 2000).
Albumin plays important function through its ability to bind various ligands.
These include free fatty acids, calcium, bilirubin and some of plasma tryptophan
(Nelson et al, 2000). Thus, albumin level is a factor to be considered in the
determination of the effect of a herb on plasma protein.
GLOBULINS
Globulins are proteins that act as
antibodies, enzymes and carrier/transport proteins (Nelson et al, 2000). Gamma
globulins are produced by mature B-lymphocytes called plasma cells while alpha
and beta globulins are made in the liver.
SEPARATION OF PLASMA PROTEINS ON THE
BASIS OF THEIR FUNCTIONS
1.
Transport and storage of molecules. Small molecules and ions are
transported by specific protein for example; Albumin transports various drugs
such as sulfonamides, penicillin G, dicumarol and aspirin.
2.
Enzymatic catalysis – most chemical reaction in biological systems are
catalyzed by specific proteins called enzymes which speed up biotransformations
e.g ALP.
3.
Co-ordination – muscle contraction occurs by the sliding motion of two
kinds of protein filament called myosin and actin.
4. Mechanical support – some proteins
contribute to the mechanical strength of some tissues in the body for example a
fibrous protein, collagen is responsible for the high tensile strength of skin
and bone in the body.
5.
Immuno globulins protection –some proteins play vital roles in immune
response in the body. Antibodies are proteins with specificity for recognizing
and attacking foreign substance in the body called antigens. Proteins also play
other major roles in transmission of nerve impulses, regulation of growth and
differentiation of cells, sources of fuel for the brain during starvation and
fasting and synthesis of biologically active molecules like hormones.
6. Blood
clothing – some proteins are involved with blood clotting. e.g. fibrinogen.