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PLASMA PROTEIN

BIOCHEMISTRY

mprasadnaidu
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PLASMA PROTEIN

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  1. PLASMA PROTEINS

  2. FLUID EXCHANGE HORMONES ENZYMES BINDING & TRANSPORT FUNCTIONS DEFENCE OF BODY NUTRITIVE BUFFER BLOOD COAGULATION VISCOSITY OF BLOOD RESERVE PROTEINS

  3. 1. NUTRITIVE FUNCTION OF PLASMA PROTEINS • Simple proteins and a good source of proteins • Macrophages split plasma proteins into amino acids for • tissue protein synthesis

  4. 2. PLASMA PROTEINS AS RESERVE PROTEINS • Occurs in following conditions • - malnutrition • - starvation • - fasting • - hypoproteinaemia • Amino acids released from broken plasma proteins • distributed throughout body to form cellular protein molecules • Used as a last source of energy

  5. 3. PLASMA PROTEINS FOR FLUID EXCHANGE • Exert colloid osmotic pressure • Play an important role in distribution of water between • blood and tissues AT ARTERIAL END OF CAPILLARIES:Hydrostatic pressure > osmotic pressure. Hence, fluid driven out of vessels into tissue spaces. Plasma proteins, however, do not leave capillaries because of their large size. AT VENOUS END OF CAPILLARIES: Osmotic pressure > hydrostatic pressure because of presence of plasma proteins in capillaries. Hence, fluid is drawn from tissue spaces into vessels. • This allows exchange of fluids and dissolved materials • between blood and tissue spaces (STARLING HYPOTHESIS)

  6. 4. PLASMA PROTEINS AS BUFFERS • Amphoteric molecules • In acidic pH. Amino group of plasma proteins combine with a proton and becomes positively charged • In alkaline medium, carboxyl group of plasma proteins donate a proton and becomes negatively charged • In this way, plasma proteins maintain a constant • pH of the medium.

  7. 5. TRANSPORT FUNCTION OF PLASMA PROTEINS • Binds to and transport various substances throughout body • Eg. 1) Albumin transport ions, drugs, penicillin, gases, • pigments, ect • 2) lipoproteins transport lipid fractions and fat-soluble • vitamins • 3) haptoglobin transport free haemoglobin • 4) transferrin transport iron

  8. 7. ROLE OF PLASMA PROTEINS IN VISCOSITY OF BLOOD • Makes blood viscous • Albumin, globulins and fibrinogen mainly responsible • Due to the large size and asymmetrical structure of • plasma proteins • Viscosity provides resistance to blood flow in vessels • This maintains blood pressure in normal range

  9. 8. PLASMA PROTEINS FOR BODY DEFENCE • Gamma-globulins also known as immunoglobulin • Act as antibodies against antigens to protect body • against infections like diphtheria, thyroid, • streptococcal infections, mumps, influenza, • measles, hepatitis, rubella, poliomyelitis, ect.

  10. 9. PLASMA PROTEINS AS ENZYMES • Enzymes are proteins (except ribozymes) • Eg. 1) Amylase • 2) transaminase • 3) dehydrogenase • 4) lipase • 5) phosphatase

  11. 10. PLASMA PROTEINS AS HORMONES • Certain hormones are proteins • Eg. 1) Oxytocin • 2) Vasopressin • 3) insulin • 4) Parathormone • 5) TSH • 6) ACTH

  12. 11. ROLE OF PLASMA PROTEINS IN BLOOD COAGULATION • Plasma contains fibrinogen, enzymes and clotting factors • These participate in coagulation of blood • Prevent excessive loss of blood during injury

  13. CLINICAL SIGNIFICANCE OF PLASMA PROTEINS

  14. HYPERPROTEINAEMIA Increase in plasma protein levels Normal plasma protein level = 6-8 g% Decrease in Plasma protein levels HYPOPROTEINAEMIA

  15. HYPERPROTEINAEMIA • Increase in total amount of plasma proteins in the body • Occurs in following 2 situations: • 1) Haemoconcentration • - due to dehydration • - both albumin and globulin are increased • - A:G ratio remains unchanged • 2) Diseases such as hypergammaglobulinaemia • - high levels of plasma globulins • - albumin level normal or reduced • - A:G ratio reversed if albumin reduced

  16. HYPERGAMMAGLOBULINAEMIA MONOCLONAL GAMMOPATHIES POLYCLONAL GAMMOPATHIES

  17. POLYCLONAL GAMOPATHIES • Chronic infections like TB, leprosy, kalaazar, etc • Chronic liver disease like cirrhosis or chronic active hepatitis • Sarcoidosis • Autoimmune diseases like rheumatoid arthritis

  18. MONOCLONAL GAMMOPATHIES BENIGN MALIGNANT • Secondary to diabetes mellitus, Chronic infections, etc • Idiopathic • Multiple myeloma • Macroglobulinaemia • Lymphoreticular malignancies • like lymphosarcoma, leukemia, • hodgkin’s disease

  19. HYPOPROTEINAEMIA Hypogammaglobulinaemia Haemodilution Hypoalbuminaemia

  20. HAEMODILUTION • Cause may be Water intoxication • Both albumin and globulin are decreased • A:G ratio remains unaltered • Results in edema because of low plasma proteins in • capillaries to exert colloid osmotic pressure

  21. HYPOALBUMINAEMIA LOSS OF ALBUMIN FROM THE BODY - RENAL: Nephrotic syndrome - GIT: Protein losing enteropathy - SKIN: Burns and other skin lesions DECREASED SYNTHESIS OF ALBUMIN - SEVERE LIVER DISEASES: cirrhosis of liver , chronic hepatitis - NON-AVAILABILITY OF PRECURSORS: Malabsorption syndrome, protein calorie malnutrition - GENETIC DEFICIENCIES: Analbuminaemia MISCELLANEOUS - Acute or chronic illnesses - infections - malignancy - pregnancy

  22. HYPOGAMMAGLOBULINAEMIA LOSS OF GAMMA-GLOBULINS FROM BODY - RENAL: Nephrotic syndrome - GIT: Protein losing enteropathy - SKIN: Burns and other skin lesions DECREASED SYNTHESIS OF GAMMA-GLOBULINS - TRANSIENT: Neonates/infants - PRIMARY: Genetic deficiency - SECONDARY: AIDS, LEUKEMIA 3) MISCELLANEOUS - Pregnancies

  23. ALBUMIN

  24. Most abundant and fairly homogeneous protein of plasma. Half of the total plasma protein is made up of albumin. Structure of Albumin.

  25. Plasma protein composition

  26. Single polypeptide chain. Contain 585 amino acids. Have 17 interchain disulfide (s-s) bonds. Molecular weight : 69 000 Low isoelectric pH (pI = 4.7) Precipitates last in salting out or alcohol precipitation method. Normal value: 3.5 – 5.5 mg/dL

  27. Normal pattern of serum proteins on electrophoresis • Normal values % of total proteins • Albumin 50 - 70 • α globulin 7 - 17 • βgobulin 7 - 16 • γ globulin 11 - 22

  28. Exclusively synthesised by the liver. Liver produces approximately 12g albumin per day which represents 25% of the total hepatic protein synthesis. Albumin has a half life of 20 days. Synthesis of albumin

  29. Albumin 67 % α helix 10 % β turn

  30. Amino acid composition

  31. TOTAL 585

  32. Osmotic Function Due to its high concentration and low molecular weight, albumin contributes to 75 – 80% of the total plasma osmotic pressure. Thus, albumin plays a predominant role in maintaining blood volume and body fluid distribution. Functions of albumin:

  33. Transport Function Plasma albumin binds to several biochemically important compounds and transports them in the circulation. These include free fatty acids which is transported to the liver, bilirubin, steroid hormones, calcium and copper.

  34. Nutritive Function Albumin serves as a source of amino acids for tissue protein synthesis to a limited extent, particularly in nutritional deprivation of amino acids.

  35. Buffering Function Among the plasma proteins, albumin has the maximum buffering capacity. Exerts low viscocity Plays an important role in exchange of water between tissue fluid and blood.

  36. Certain drugs also bind to albumin. e.g sulphonamides, aspirin, penicillin. These drugs are directly transported to the target organ.

  37. Clinical significance • Hypoalbuminemia • Hyperalbuminemia

  38. Occurs due to a decrease in concentration of albumin, i.e when it is less than 2.5 gm% Hypoalbuminemia

  39. Loss from the body Loss of albumin in urine in nephrotic syndrome In burns, albumin is loss through the unprotected skin surface. (2) Decreased synthesis of albumin • Severe liver diseases: chronic hepatitis, cirrhosis liver. • Non-availability of the precursor: malabsorption syndrome, protein calorie malnutrition • Genetic deficiency: Analbuminaemia (3) Others • Chronic illness • Infections • Malignancy • pregnancy Causes

  40. Decrease in albumin concentration leads to oedema formation. Oedema is a situation where tissue swelling takes place.

  41. increasing blood protein level in patient with a nutritional deficiency. Diuretic treatment – kidney is made to excrete excess fluid from the body. Treatment of oedema:

  42. Occur when albumin level is high, i.e greater than 5.5 gm% Seen in the absence of dehydration. Frequent in obese men. hyperalbuminemia

  43. Classification of plasma protein. Functions of plama protein. Albumin. Clinical significance. Summary

  44. Wikipedia Textbook of medical physiology – MN Chatterjea, RanaShinde google images Bibliography

  45. Thank you for your attention....

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