Plasma proteins for Medical students

1. PLASMA PROTEINS-II
Prof. Dr. Viyatprajna Acharya

2. BLOOD
PLASMA
SERUM
WHAT’STHE DIFFERENCE?

3. Total blood volume: 4.5-5 lit
Whole blood left to clot centrifuged
Supernatant is ‘SERUM’
Blood+ Anticoagulant centrifuged
Supernatant is ‘PLASMA’
55-60% of BLOOD- PLASMA
Defibrinated plasma = Serum

4.  Total plasma protein content- 6-8 gm/dl
 Hundreds of different proteins in plasma
 Important ones:
Albumin
Globulin
Fibrinogen
Clotting factors
Transferrin
Ceruloplasmin; etc

5. Albumin- 3.5-5 gm/dl
Globulin- 2.5-3.5 gm/dl
Fibrinogen- 200- 400 mg/dl
A: G ratio – 1.2:1 to 1.5: 1
Almost all proteins except Immunoglobulins
synthesized in liver

6. Comparisonofsizes

7. Around300plasmaproteins
Important ones:
1. Albumin
2. Globulin
3. Fibrinogen
4.Transport proteins
5. Immunoglobulins
6. Clotting factors
7. Acute phase proteins

10. Most abundant in plasma
Found in extra-vascular fluids
One polypeptide chain
585 AA; 17 disulfide bonds
Synthesized by hepatocytes
12g/day produced
T1/2 is 15-19 days
Over 80 allelic forms available

11. Functionsofalbumin
Exerts osmotic pressure- effective osmotic pressure
(25mm Hg)
80% exerted by albumin
Transport- Bilirubin
NEFA
Drugs
Steroid hormones
Calcium
Copper
Heavy metals

12. Buffering action- 16 His residues
Nutritional function-contributes to essential AA
pool

13. Clinicalsignificance
HYPERALBUMINEMIA: Rare and insignificant;
Dehydration
HYPOALBUMINEMIA:
Cirrhosis of liver
Malnutrition
Acute inflammation
Burns
Nephrotic syndrome
Albuminuria
Protein losing enteropathy
ANALBUMINEMIA: rare genetic defect; albumin<
0.5g/dl; mild edema

14. Pre-albumin
 Minor band running ahead of Albumin
 TBPA (Thyroxin binding prealbumin)
 RBPA(Retinol binding prealbumin)
 Low levels: Hepatitis
Early cirrhosis
Thyrotoxicosis
Deficiency of Zn

15. Globulins

16. Alpha 1 Proteins
 Alpha-1-Lipoprotein-HDL
 Alpha-1-Antitrypsin
-- Protease inhibitor(Particularly Elastase) that
binds to and inactivates trypsin
– Deficiency leads to destruction of the alveolar
walls and is associated with pulmonary
deficiency- Emphysema
– Deficiency also seen in cirrhosis
– Alpha-1-antitrypsin is an acute phase protein and
is increased in acute episodes of tissue damage

17.  α1-Acid glycoprotein (orosomucoid) -
 45% carbohydrate
 Synthesized by hepatocytes
 Binds and inactivates lipophilic and basic
hormones e.g. Progesterone
 Acute phase protein
 ↑ levels- pregnancy, ulcerative colitis
• α1-Fetoprotein (AFP)
 Principal foetal protein, used to screen for foetal
abnormalities (neural tube defects)
 Tumor marker for hepatocellular and germ cell
carcinomas
 ↓levels- fetal trisomy 18 or 21

18. α2 Globulins
 Ceruloplasmin
 Cu containing
 6-8 Cu per molecule
 Regulation of oxidation-reductions, transport
and utilization of iron
 ↓level- Wilson’s hepatolenticular degeneration

19.  Transcortin/ Corticosteroid binding
globulin- Binds cortisol
↑ synthesis by estrogen
 Haptoglobin- Conservation of iron
 Thyroxin binding globulin- TransportsT3
&T4
 α2 Macroglobulin- natural inhibitor of
endopeptidase such as trypsin, chymotrypsin,
plasmin, thrombin- in vivo anticoagulant
- ↑level- Nephrotic syndrome, cirrhosis, collagen
disorder
- ↓ level- Myeloma, peptic ulcer

20. β-Globulin
 Haemopexin- Binds to free heme and
conserves
 Transferrin-Transports iron
↑ level- Fe deficiency anemia, Pregnancy
↓ level- Chr. Infections, malnutrition
 β2- Microglobulin- part of HLA
↑level- malignant lymphoid or myeloid
proliferation , Renal failure

21.  C-reactive protein (CRP)- reacts with c-
polysaccharide of cell wall of pneumococci
- ↑level- bacterial infections
-hs-CRP- predicts the risk of coronary disease

22. γ-Globulins
 Immunoglobulins - 5 major classes

23. Acutephaseresponse&acutephaseproteins
 Non-specific response to the stimulus of tissue
following trauma, infection, inflammation and
burn etc.– ACUTE PHASE RESPONSE
 ACUTE PHASE PROTEINS-- ↑ levels within few
hours of assault
CRP
Ceruloplasmin
α1 Antitrypsin
α1 acid glycoprotein
Haptoglobin
Fibrinogen etc.

24. NEGATIVEACUTEPHASEREACTANTS/
PROTEINS
 ↓ level in inflammatory processes
Albumin
Prealbumin
Retinol binding protein
Transferrin

25. After silence, that which comes nearest to expressing the inexpressible is music.
Aldous Huxley