Dr. Nasim AP Biochemistry Plasma Proteins Dr. Nasim AP Biochemistry

Plasma Proteins Synthesized by liver or produced by plasma (B) cells Albumin Transferrin Ceruloplasmin Enzymes – Coagulation enzymes, complement factors C-reactive protein – Acute phase reactant Immunoglobulins – Humoral immunity Transport proteins

ALBUMIN 66 kDa Accounts for ~50% of the total plasma protein and ~ 50% of the total liver protein production  Half-life ~ 20 days  Highly polar  At pH 7.4 it is anionic with 20 negative charges per molecule

Causes of Decreased Plasma Albumin: Decreased synthesis A. Malnutrition B. Malabsorption C. Advanced chronic liver disease II. Abnormal distribution or dilution A. Overhydration B. Increased capillary permeability like in septicemia Abnormal excretion or degradation A. Nephrotic syndrome B. Burns C. Hemorrhage D. Certain catabolic states E. Loss of protein from the digestive tract Rare congenital defects A. Hypoalbuminemia

Regulation of Colloidal Pressure Gaw: Clinical Biochemistry; Churchill Livingstone (1999), p. 44.

Plasma Proteins Globulins Fibrinogen 36% of plasma proteins alpha and beta produced in liver proteins that bind to lipids, metal ions and fat-soluble vitamins gamma - antibodies produced by plasma cells during immune response Fibrinogen 4% of plasma proteins produced in liver forms fibrin threads during clotting

TRANSFERRIN Transports iron in plasma as ferric ions (Fe3+) – each Transferrin molecule binds 2 Fe3+ Protects the body against the toxic effects of free iron Normally 30% saturated with Fe3+ - increased or decreased saturation is indicative of iron overload or deficiency, respectively  Decreased in inflammatory states due to excessive degradation of Transferrin- Fe3+ complexes

CERULOPLASMIN Major copper transport protein  Regulates oxidation-reduction, transport and utilization of iron Increased concentrations are found in active liver disease or tissue damage Decreases are sometimes observed in individuals with Wilson’s disease

Plasma Proteins Functions 1. Maintaining colloid osmotic balance (albumins) 2. Buffering pH changes 3. Transport of materials through blood (such as water insoluble hormones) 4. Antibodies (e.g. gamma globulins, Immunoglobulins) 5. Clotting factors (e.g. fibrinogen)