Plasma proteins

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Plasma Proteins
R. C. Gupta Professor and Head Dept. of
Biochemistry National Institute of Medical
Sciences Jaipur, India
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EMB-RCG
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E M B - R C G
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E M B - R C G
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Fractionation of plasma proteins
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Plasma proteins are usually fractionated by
electrophoresis
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E M B - R C G
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More sensitive techniques separate the
b-globulins into b1- and b2-globulins
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E M B - R C G
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Albumin
Most abundant protein in plasma
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Concentration is 3.5 - 5.5 gm/dl
Synthesized exclusively in liver
Half-life approximately 20 days
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Proteins are the major colloids in plasma
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COP of plasma is mostly due to proteins
Albumin is responsible for 75 of COP of plasma
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E M B - R C G
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Hypoalbuminaemia can occur in
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Hypoalbuminaemia decreases the colloid osmotic
pressure of plasma
This can result in oedema
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Prealbumin
Another protein that can bind all the
ligands that albumin can bind
Smaller than albumin and moves ahead of albumin
on electrophoresis
Present in much lower concentration
than albumin
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Globulins
E M B - R C G
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a1-Globulins
E M B - R C G
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E M B - R C G
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a1-Antitrypsin
E M B - R C G
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E M B - R C G
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An inherited deficiency of a1-antitrypsin results
in unchecked action of elastase on elastin
E M B - R C G
Destruction of elastin decreases the elasticity
of lungs resulting in emphysema
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Smokers with a1-antitrypsin deficiency are
particularly prone to emphysema
Cigarette smoke converts a critical methionine
residue of a1-antitrypsin into methionine
sulphoxide
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This prevents the binding of a1-antitrypsin to
elastase
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E M B - R C G
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Release of acute phase proteins is induced by
some interleukins secreted by macro-phages and T
lymphocytes
E M B - R C G

Acute phase proteins help the
immune system in fighting against infectious
agents

They also help in clearing
up the debris from the site of infection
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a-Fetoprotein

a-Fetoprotein
(AFP) is synthesized in foetal life but not
after birth
E M B - R C G

It is synthesized in
some cancers as the cancer cells revert to the
undifferentiated type
Therefore, a-fetoprotein is used as a tumour
(cancer) marker
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a2-Globulins
E M B - R C G
EMB-RCG
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Ceruloplasmin
A copper-containing protein
E M B - R C G
90 of plasma copper is tightly bound
to ceruloplasmin
Rest is loosely bound to albumin
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E M B - R C G
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E M B - R C G
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Haptoglobin
Another acute phase protein
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Can bind free haemoglobin (Hb)
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E M B - R C G
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E M B - R C G
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a2-Macroglobulin
E M B - R C G
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b-Globulins
E M B - R C G
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E M B - R C G
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Haemopexin
E M B - R C G
This can lead to loss of iron from the body
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E M B - R C G
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C-Reactive protein (CRP)
So named because it reacts with C polysaccharide
E M B - R C G
C Polysaccharide is present in the capsule of
pneumococci
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CRP is an acute phase protein
It can stimulate the classic complement cascade
upon entry of any pathogen in the body
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Raised CRP concentration in plasma shows the
presence of some infection in the body
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g-Globulins
E M B - R C G
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Fibrinogen
Is an acute phase protein
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Is converted into fibrin during
coagulation
Several fibrin molecules aggregate to
form the clot
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Fibrinogen
Fibrin monomer
Fibrin dimer
Fibrin polymer
Fibrin polymer cross-linked
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Thank you