Plasma Proteins Reading assignment Harper’s Biochemistry: PP 737-745

1. Plasma ProteinsReading assignment Harper’s Biochemistry: PP 737-745 Dr. Zeyad El-Akawi Jreisat, M.D, M.A, Ph.D

2. Blood • Solid elements: • Red cells • White cells • Platelets • Liquid medium: • Plasma

3. Blood

4. Major Functions of Blood - Respiration - Nutrition - Excretion - Acid-base balance - Water balance - Body temperature regulation - Defense - Hormone transport and regulation of metabolism - Metabolite transport - Coagulation

5. Difference between plasma and serum???? Serum = plasma - coagulation factors

6. Plasma Composition • Water 92% • Plasma proteins 7% (total 7.0-7.5 g/dL) • Simple • Conjugated • Glycoproteins • Lipoproteins • Electrolytes (Na+, K+, Ca+2, Cl-, HCO3-) • Metabolites • Nutrients • Hormones • Other solutes 1%

7. Plasma proteins • Most plasma proteins, with the exception of immunoglobulins and protein hormones are synthesized in the liver • Plasma proteins are generally synthesized on membrane-bound polyribosomes • Rough endoplasmic membrane → smooth endoplasmic membrane → Golgi apparatus → secretory vesicles → Plasma • Almost all plasma proteins are glycoproteins • Plasma proteins circulate in the blood and between the blood and the extra-cellular tissue spaces. Their movement occurs not only by passive diffusion through junctions between capillary endothelial cells but by active transport mechanisms and by pinocytosis and exocytosis

8. Plasma proteins • Because of this movement, most extra-vascular fluids normally contain small amount of plasma proteins • The concentration of protein in the plasma is important in determining the distribution of fluid between blood and tissues • Many plasma proteins exhibit polymorphism • Alpha1-antitrypsin, haptoglobin, transferrin, ceruloplasmin and immunoglobulins • Each plasma protein has a characteristic half-life in the circulation • Most plasma proteins are catabolized in the liver.

9. Plasma proteins • Alterations in plasma proteins occurs in health and disease • The levels of certain proteins in plasma increase during acute inflammatory states or secondary to certain types of tissue damage • Some of these alterations have genetic origin, many more reflect physiological or pathological processes • Variations in the amount or kinds of protein found in plasma or extra-vascular fluids depend on many factors • Genetic • Physiological • Pathological

10. Classification of plasma proteins based on their function • Antiproteases: antichymotrypsin, alpha1-antitrypsin, alpha2-macroglobulin, antithrombin • Blood clotting: various coagulation factors, fibrinogen • Enzymes: • Function in blood; coagulation factors, cholinesterase • Leakage from cells or tissues; aminotransferases • Hormones: Erythropoietin • Immune defense: immunoglobulins, complement proteins, beta2-microglobulin • Involvement in inflammatory responses: Acute phase response proteins (c-reactive proteins, alpha1-acid glycoprotein) • Oncofetal: alpha-1 fetoprotein (AFP)

11. Classification of plasma proteins based on their function • Transport or Binding proteins: • Albumin; various ligands, including bilirubin, free fatty acids, ions (Ca+2), metals (Cu+2, Zn+2), metheme, steroids and other hormones, drugs. • Ceruloplasmin: contains Cu+2 • Corticosteroid-binding globulin: transcortin (binds cortisol) • Haptoglobin: binds extracorpuscular hemoglobin • Lipoproteins: chylomicrons, VLDL, LDL, HDL • Hemopexin: binds heme • Ritenol-binding protein: binds retinol • Sex hormone-binding globulin: binds testosterone, estradiol • Thyroid-binding globulin: binds T3, T4 • Transferrin: transport iron • Transthyretin (prealbumin): binds T4 and forms a complex with retinol-binding protein

12. Plasma proteins separation • Separation of individual proteins from a complex mixture is accomplished by the use of solvents or electrolytes or both to remove different protein fractions in accordance with their solubility characteristics. • Salting out: a method for separation of plasma proteins using various concentrations of [Sodium or ammonium sulfate] • Plasma proteins can be separated by this method into three groups • Fibrinogen • Albumin • Globulins

13. Plasma proteins separation • Electrophoresis: • The most common method of analyzing plasma proteins • Using different supporting medium, the most common in clinical laboratories is cellulose acetate (electrophoretogram) • Separated proteins into five bands: albumin, alpha1, alpha2, beta, and gamma fractions • The amount of bands quantified by densitometric scanning machine

14. Electrophoresis

15. Plasma protein electrophoresis

16. Quantified of plasma proteins by densitometric scanning machine

18. Plasma proteins separation • Antibodies: • Specific plasma proteins are separated by specific monoclonal antibodies fixed on stationary phase (Column Chromatography) • Allowing isolation of pure proteins from the complex mixture present in plasma

19. Acute phase reactant proteins **Concentration of these proteins rise significantly in acute inflammation, chronic inflammation and cancer** • Alpha1-antitrypsin (AAT): congenital deficiency may be associated with emphysema or cirrhosis • Alpha1-acid glycoprotein (AAG): binds cationic drugs and hormones • Haptoglobin (HAP): binds hemoglobin, reduced by hemolysis • Ceruloplasmin (CER): contains copper, antioxidant, decreased in Wilson’s disease • C4: Complement factor • C3: Complement factor • C-reactive protein (CRP): Nonspecific defense against infectious agents • Fibrinogen **Stimulatory factors, Interleukin-1 (IL-1) and interleukin-6 (IL-6) at the gene level**

20. Plasma proteins • Albumin: • is the major protein of human plasma (3.4-4.7 g/dL) • Approximately 40% of albumin is present in plasma and the other 60% in the extracellular space • It synthesized in the liver as preproprotein • The synthesis of albumin is depressed in a variety of diseases, particularly those of the liver (decreased albumin/globulin ratio) • Responsible for 75-80% of the osmotic pressure of human plasma • Absence of albumin (analbuminemia) might caused by mutation that affect splicing • It binds many ligands (free fatty acids, calcium, certain steroid hormones, bilirubin, tryptophan) • It binds and transport drugs (sulfonamides, penicillin G, dicumarol, aspirin) • It transports copper

21. Haptoglobin: • Binds extracorpuscular hemoglobin preventing free hemoglobin from entering the kidney • Exist in three polymorphic forms, Hp1-1, Hp2-1, Hp2-2 • Low levels of haptoglobin are found in patients with hemolytic anemias • It is an acute phase protein and its plasma level is elevated in a variety of inflammatory states • Transferrin: • Is a beta-1 globulin • It is a glycoprotein synthesized in the liver • Shuttles iron to sites where it is needed • Transferrin diminishes the potential toxicity of iron • The concentration of transferrin in plasma is approximately 300 mg/dL that can bind 300 µg of iron per deciliter (total iron-binding capacity) of plasma

22. Ferritin: • Normally there is a little ferritin in human plasma • In patients with excess iron, the amount of ferritin in plasma is markedly elevated • Index of body iron stores • Synthesis of the transferrin receptors and that of ferritin are reciprocally linked to cellular iron content • Iron response elements • Iron-responsive element-binding protein • Hemosiderin: • Partly degraded form of ferritin but still containing iron • Primary hemochromatosis: is a common genetic disorder characterized by excessive storage of iron in tissues leading to tissue damage • Secondary hemochromatosis: can occurs in the result of increased iron levels by transfusion, intake, hemolysis

23. Ceruloplasmin: • It is an alpha-2 globulin • Binds copper • Low levels of this protein are associated with Wilson disease • It exhibits a copper-dependent oxidase activity • Copper: • Is a cofactor for certain enzymes including, amine oxidase, copper-dependent superoxide dismutase, cytochrome oxidase, tyrosinase • It is excess can cause problems because it can oxidize proteins and lipids, bind to nucleic acids and enhance the production of free radicals • Metallothioneins: are a group of small proteins found in the cytosol of cells particularly of liver, kidney, and intestine they control of copper levels

24. Menkes Disease: “kinky” or “Steely” hair disease • Is due to mutations in the gene for a copper-binding P-type ATPase leads to abnormality in copper metabolism • X-linked • Defect in copper exit from cells leads to its accumulation • Involves the nervous system, connective tissue and vasculature • Wilson Disease: • Is due to mutations in the gene for a copper-binding P-type ATPase results in the failure of copper to be excreted in the bile • Copper toxicoses • Alpha-1 antitrypsin deficiency: a serine protease inhibitor • Is associated with emphysema and liver disease • Synthesized by hepatocytes and macrophages