PRESENTED TO:MA’AM MUDASSARA HAROON

PLASMA PROTIENS AND THEIR CLINICAL

SIGNIFICANCE

CONTENTS

• INTRODUCTION

• WHAT ARE PLASMA PROTIENS?

• COMPOSITION OF BLOOD

• PLASMA AND SERUM

• MAJOR PLASMA PROTIENS

• STRUCTURES

• FUNCTIONS

• CLINICAL SIGNIFICANCE

INTRODUCTION

This presentation is extensively about plasma proteins , their

functions, structures and clinical aspects .every plasma

protein has been discussed specificly to learn its clinical

significance

WHAT ARE PLASMA PROTIENS?• Plasma proteins are proteins found in the blood

plasma, the clear, protein-rich fluid which is left behind when platelets, red blood cells, and white blood cells are removed from the blood.

• These proteins play a number of important roles in the human body, and levels of plasma proteins are sometimes evaluated in a laboratory analysis to gather information about a patient's general health.

• These proteins make up around 7% of the total blood volume, with levels which can fluctuate at times.

COMPOSITION OF BLOOD

Blood is made up of an aqueous liquid (plasma) in which solids (blood cells, platelets) are suspended. It accounts for 7% to 8% of the body’s weight.

PLASMA AND SERUM

• Plasma is composed of serum and clotting factors.

• Serum is the part of blood which lack clotting factors.

• Plasma – clotting factors = Serum

GENERAL FUNCTIONS

• ROLE IN COAGULATION OF BLOOD

• ROLE IN DEFENSE MECHANISM OF BODY

• ROLE IN TRANSPORT MECHANISM

• ROLE IN MAINTENANCE OF PRESSURE IN BLOOD

• ROLE IN REGULATION OF ACID BASE BALANCE

• ROLE IN VISCOSITY OF BLOOD

• ROLE AS RESERVE PROTEINS

MAJOR PLASMA PROTIENS

ALBUMINS 58%

GLOBULINS 38%

FIBRINOGEN 4%

ALBUMINS• It is the most abundant and fairly homogenous

protein of plasma, with a molecular weight of 69,000.

• Approximately half of the total proteins of plasma is albumin.

• It has a low pH (pH = 4.7).

• About 40% of albumin is present in the plasma, and the other 60% is present in the extracellular space.

• Half life of albumin is about 20 days.

SYNTHESIS OF PROTIENS

• Albumin is mainly synthesised in liver.

• Rate of synthesis is approx. 14.0 gms/day.

• Albumin is initially synthesized as a “Preproprotein”.

• Its signal peptide is removed as it passes into the cisternae of the rough endoplasmic reticulum, and a hexapeptide at the resulting aminoterminal is subsequently cleaved off further along the secretory pathway.

STRUCTURE OF ALBUMIN

• It is a simple protein, consisting of a singlepolypeptide chain, having 585 amino acids,

• having 17 interchain disulphide (S–S) bonds.

• The molecule is ellipsoidal in shape, measuring 150Å × 30Å.

FUNCTIONS OF ALBUMIN• It exerts low viscosity.

• Contributes 70 to 80% of osmotic pressure and plays an important role in exchange of water between tissue fluid and blood.

• Also undergoes constant exchange with the albumin present in extracellular spaces of muscles, skin and intestines.

• Helps in transport of several substances viz. FFA (NEFA/UFA), unconjugated bilirubin, Ca++ and steroid hormones.

• Certain drugs also bind to albumin, e.g. sulphonamides, aspirin, penicillin, etc. and are transported to target tissue.

CONTINUED• Nutritive function: Albumin in plasma is in a

dynamic state with a rapid turnover with a specific half-life. It is delivered to cells where it is hydrolysed and cellular proteins are synthesised

• It plays a predominant role in maintaining blood volume and body fluid distribution.

• Buffering Function-Among the plasma proteins, albumin has the maximum buffering capacity due to its high concentration and the presence of large number of histidine residues, which contribute maximally towards maintenance of acid base balance.

CLINICAL SIGNIFICANCE

• Decrease in albumin concentration: Concentration of albumin decreases in severe protein calorie malnutrition (PCM), liver diseases like cirrhosis of liver, (albumin synthesis impaired), nephroticsyndrome (albumin is lost in urine).

• Decrease in albumin concentration leads to oedema formation.

• Oedema occurs when total proteins fall below about 5.0 gm% and albumin level below approx. 2.5 gm%.

CONTINUED

• Blood brain barrier- Albumin- free fatty acid complex can not cross the blood brain barrier, hence fatty acids can not be utilized by the brain.

• Loosely bound bilirubin to albumin can be easily replaced by drugs like aspirin.

• In new born if such drugs are given, the released bilirubin gets deposited in brain causing Kernicterus.

CONTINUED

• Protein bound calcium

• Calcium level is lowered in conditions of Hypo- Albuminemia

• Serum total calcium may be decreased

• Ionic calcium remains same

• Tetany does not occur

• Calcium is lowered by 0.8 mg/dl for a fall of 1g/dl of albumin

CONTINUED

• Drug interactions—

• Two drugs having same affinity for albumin when administered together, can compete for available binding sites with consequent displacement of other drug, resulting in clinically significant drug interactions.

• Example-Phenytoin, dicoumarolinteractions

CONTINUED• Edema- Hypoalbuminemia results in fluid retention in the tissue

spaces

• Normal level- 3.5-5 G/dl

• Hypoalbuminemia- lowered level is seen in the following conditions-

• Cirrhosis of liver

• Malnutrition

• Nephrotic syndrome

• Burns

• Malabsorption

• Analbuminemia- congenital disorder

• Hyperalbuminemia- In conditions of fluid depletion(Haemoconcentration)

GLOBULINS

• molecular weight ranges from 90,000 to 13,00,000.

α1-globulins

α2-globulins

β-globulins

Y-globulins

SITE OF SYNTHSIS• α and β globulins are synthesized in the liver.

• Y globulins are synthesized in plasma cells and B-cells of lymphoid tissues (Reticulo-endothelial system).

• Synthesis of Y globulins is increased in chronic infections, chronic liver diseases, auto immune diseases, leukemias, lymphomas and various other malignancies.

Α-GLOBULINS

• They are glycoproteins and are further classified into α1 and α2 depending on their electrophoretic mobility.

TYPES• α1antitrypsin

• α1 acid glycoprotein (Orosomucoid)

• α1-fetoprotein (AFP)

• α1 globulins inhibitors

Α1 ACID GLYCOPROTEIN(OROSOMUCOID)

• Also called as orosomucoid.

• Concentration in normal plasma is 0.6 to 1.4 gm per litre (average = 0.9).

• Its carbohydrate content is about 41 percent. Orosomucoid is considered to be a reliable indicator of acute inflammation.

FUNCTION

• Orosomucoid binds the hormone progesterone and functions as a transport protein for this hormone.

• Probably serves to carry needed carbohydrate constituents to the sites of tissue repair following injury, since it has a high carbohydrate content (41%).

CLINICAL SIGNIFICANCE

• Increase: Consistently rises in acute and chronic inflammatory diseases, in cirrhosis of the liver and in many malignant conditions.

• Decrease: Low concentrations (abnormally low) occurs in generalisedhypoproteinaemic conditions, viz. hepatic diseases, cachexia, malnutrition and in nephrotic syndrome.

Α1-FETOGLOBULIN

• It is present in high concentrations in foetal blood during mid-pregnancy.

• Normal adult blood has less than 1 μg/100 ml. It may increase during pregnancy

CLINICAL SIGNIFICANCE

Presence of α1-fetoprotein is useful diagnostically in determining presence of hepatocellular carcinoma or teratoblastomas (tumour marker).

Α1-GLOBULINS INHIBITORS

Some of the α1-globulins act as inhibitors of coagulation and also inhibit some digestive enzymes like trypsin and chymotrypsin.

Α1-ANTITRYPSIN (Α1-AT)• Molecular weight: approx. 45,000 to 54,000

• Normal value in adults: 2 to 4 gm/Litre(approx.290 mg/ml).

• The protein is highly polymorphic, the multiple forms can be separated by electrophoresis.

• It is synthesised by liver and it is the principal protease

• inhibitor (Pi) of human plasma.

• It inhibits trypsin, elastaseand certain other proteases by forming complexes with them.

CLINICAL SIGNIFICANCE• Increases of serum α1-antitrypsin: In response

to inflammation; acute, subacute and chronic.

• It is considered as one of the acute phase reactant and increased in trauma, burns, infarction, malignancy, liver disease, etc. Chronic hepatocellular diseases and biliaryobstruction, either normal or increased. In pregnancy and also during contraceptive medication. Neonates have serum concentrations much below adult values, but show gradual increase with age and achievement of adult levels is rapid.

• Decreases in serum α1-antitrypsin: In protein losing disorders, e.g. nephrotic syndrome, diffuse hypoproteinaemias, in emphysema of lungs and in juvenile cirrhosis liver.

CONTINUED…• Role in Emphysema Lung: A deficiency of α1-AT has a

role in certain cases, approx. 5 per cent, of emphysema of lung. This occurs mainly with ZZ phenotype who synthesise PiZ.

• Normally α1-AT protects the lung tissues from injurious effects by binding with the proteases, viz. active elastase.

• A particular methionine (358 residue) is involved in binding with the protease.

Active elastase + α1-AT

↓

Inactive elastase: α1-AT complex

↓

No proteolysis of lung __________ No tissue damage

CONTINUED…

• When α1-AT is deficient or absent the above complex with active elastase does not take place and active elastase brings about proteolysis of lung and tissue damage.

Active elastase + No or ↓ α1-AT

↓

Active elastase _________ proteolysis of lung

(complex does not form) ↓

Tissue damage

CONTINUED…

• Relation of smoking with emphysema: Smoking oxidises the methionine (358 residue) of α1-AT and thus inactivates the protein, hence such α1-AT molecule cannot bind to the protease ‘active elastase’ and thus proteolysis of lung and tissue damage occurs accelerating the development of emphysema.

CONTINUED…

• Role as a tumour-marker: α1-AT has been used as a tumour marker. It is increased in germ cell tumours of testes and ovary.

• As an Inhibitor of Fibrinolysis: α1-AT is one of the most important inhibitors to fibrinolysis along with α2-antiplasmin and α2-macroglobulin. All these inhibitors block the action of plasmin on fibrinogen.

CONTINUED…• Role in cirrhosis: Juvenile hepatic

cirrhosis has also been correlated with α1-AT deficiency. In this condition molecules of PiZ (ZZ phenotype) accumulate and aggregate in the cells of the cisternae of the endoplasmic reticulum of hepatocytes.

• The hepatocytes cannot secrete this particular type of α1-AT. Thus PiZ protein of α1-AT is synthesisedbut not released from the hepatocytes.

• The aggregates lead to damage to liver cells leading to hepatitis and cirrhosis—accumulation of massive amount of collagen resulting to fibrosis.

Α2-GLOBULINS

• Clinically important α2-globulins are-

HAPTOGLOBULIN

CAERUPLASMIN

CAERUPLASMIN• It is a copper containing α2-globulin, a glycoprotein

with enzyme activities. Molecular weight is ≈ 151,000.

• It has eight sites for binding copper-contains about eight atoms of copper per molecule-½ as cuprous(Cu+) and ½ as cupric (Cu++).

• It carries 0.35 percent Cu by weight.

• Normal plasma contains approx. 30mg/100 ml and about 75 to 100 μg of Cu may be present in 100 ml of plasma.

• It has enzyme activities,e.g. copper oxidase, histaminaseand ferrous oxidase.

• There is low concentrations at birth, gradually increases to adult levels, and slowly continues to rise with age thereafter.

CLINICAL SIGNIFICANCE• Although caeruloplasmin is not involved in copper

transport, 90 per cent or more of total serum copper is contained in caeruloplasmin.

• It mainly functions as a ferroxidase and helps in oxidation

• (conversion) of Fe++ to Fe+++ which can be incorporated

• into transferrin.

• Increase: It is found in pregnancy, inflammatory processes,malignancies, oral oestrogen therapy and contraceptive pills.

• Decrease: In Wilson’s disease(hepatolenticulardegeneration) and in Menke’s disease.

HAPTOGLOBULIN

• It is composed of two kinds of polypeptide chains, two α-chains (possibly three) and only one form of β-chain.

• It is synthesised principally in liver by hepatocytes and to a very small extent.

• Haptoglobin (Hp) increases from a mean concentration of 0.02 gm/L at birth to adult levels (10×) within the first year of life.

• As old age approaches, haptoglobin level increases, with a more marked increase being seen in males.

FUNCTIONS• The function of haptoglobin is to bind free Hb by

its α-chain and minimises urinary loss of Hb. Abnormal Hb such as Bart’s-Hb and Hb-H have no α-chains and hence cannot be bound.

• Combining power of Hp with free Hb varies with different phenotypes. Average binding capacity of Hp, irrespective of phenotype, can be taken approx. as 100 mg/dl.

• After binding, Hp-Hb complex circulates in the blood, which cannot pass through glomerularfilter and ultimately the complex is destroyed by RE cells.

CLINICAL SIGNIFICANCE

• Serum Hp concentration is found to be increased in inflammatory conditions.

• Determination of free Hp (or Hp-binding capacity) has been used to evaluate the degree of intravascular haemolysis which can occur in mismatched blood transfusion reactions and in haemolytic disease of the newborn (HDN).

• Used also to evaluate the rheumatic diseases.

BETA GLOBULINS

• Globulins of clinical importance are –

C-reactive protein

Transferrin

Complement C1q

Haemopexin

TRANSFERRIN• It is non-heme iron-containing protein and formerly used to

be called as siderophilin.

• It exists in plasma as β1-globulin, a glycoprotein with molecular weight 70,000 approximately and it is a true carrier of Fe.

• Its concentration in normal plasma is 1.8 to 2.7 gm/litre(average 2.3gm/litre). It has capacity to bind 3.4 mg of Fe per litre or 1.46 mg of Fe+++ per Gm of transferrin.

• Normally transferrin is about 33 per cent saturated with Fe.

• The protein is synthesised principally and largely in liver. There is also evidence of its synthesis in bone marrow, spleen, and lymph nodes, perhaps by lymphocytes.

CLINICAL SIGNIFICANCE• Sole function is the transport of Fe between

intestine and site of synthesis of Hb and other Fe containing proteins.

• Recently it has also been seen that unsaturated transferrin has a bacteriostatic function which is attributed to sequestration of Fe required by microorganisms.

• Increase: Serum transferrin levels are seen increased in Iron deficiency anaemia and in last months of pregnancy.

• Decrease: Parallels to albumin in conditions like protein calorie malnutrition (PCM), cirrhosis of the liver, nephrotic syndrome, acute illness such as trauma, myocardial infarction and malignancies or other wasting diseases.

C-REACTIVE PROTIEN

• It is present in concentration less than 1 mg/100 ml in the adult male.

• It precipitates with group C polysaccharide of pneumococci, in the presence of Ca++, hence it is named as “C-reactiveprotein”.

CLINICAL SIGNIFICANCE• It can bind heme and bears some chemical and

antigenic relation to liver catalase.

• It can bind to T-lymphocytes and can activate complement.

• A role in the formation of heme proteins or as an ‘opsonin’in augmenting immunity has been proposed.

• It is a sensitive, if not non-specific, indicator of the early phase of an inflammatory process.

• • It remains increased in presence of solid tumours, but not in conditions which impair immune response such as leukaemias or Hodgkin’s disease.

HAEMOPEXIN

• Molecular weight: 57,000 to 80,000. Normal value in adults = 0.5 to 1.0 gm/L.

• The level of hemopexin is very low at birth but reaches adult values within the first year of life.

• It is synthesised by parenchymalcells of liver.

CLINICAL SIGNIFICANCE• The principal function of haemopexin is to bind and remove

circulating haem which is formed in the body from breakdown of Hb, myoglobin or catalase.

• It binds heme (ferroprotoporphyrin IX) and several other porphyrins in 1: 1 ratio.

• The haemhaemopexin complex is removed by the parenchymal cells of liver.

• Decrease: (i) In haemolytic disorders, serum hemopexin is decreased, (ii) At birth in newborns, (iii) Administration of diphenylhydantoin.

• Increase: (i) Pregnant mothers have increased serum levels, (ii) In diabetes mellitus, (iii) Duchenne muscular dystrophy, (iv) Some malignancies, especially melanomas.

COMPLEMENT C1Q• Complement is a collective term for several

plasma proteins that are precursors for certain active proteins circulating in blood.

• These proteins participate in immune reaction in the body.

• After the formation of immune complexes, C1q is the first complement factor that is bound.

• It is thermolabile and is destroyed by heating at 56°C × ½ hour, normal value in adult 0.15 gm/L, Mol. wt 400,000, it can bind heparin and bivalent ions such as Ca++.

CLINICAL SIGNIFICANCE

• Decrease: Decrease in plasma C1q concentration is used as an indicator of circulating antigen-antibody complexes.

• Thus levels are decreased: In active immune disease such as SLE, (i) In disorders of protein synthesis, (ii) In ncreased protein loss in intestinal diseases.

• Increase: Levels are increased (i) In certain chronic infections (ii) In rheumatoid arthritis.

Y-GLOBULINS

• They are immunoglobulins with antibody activity

• They occupy the gamma region on electrophoresis

• Immunoglobulins play a key role in the defense mechanisms of the body

• There are five types of immunoglobulins IgG, IgA, IgM, IgD, and IgE.

MAJOR FUNCTIONSPROTIEN

FUNCTION

IgG Main antibody in the secondary response. Opsonizesbacteria, Fixes complement, neutralizes bacterial toxins and viruses and crosses the placenta.

IgA Secretory IgA prevents attachment of bacteria and viruses to mucous membranes. Does not fix complement.

IgMProduced in the primary response to an antigen. Fixes complement. Does not cross the placenta. Antigen receptor on the surface of B cells.

IgD Uncertain. Found on the surface of many B cells as well as in serum.

IgE Mediates immediate hypersensitivity Defends against worm infections. Does not fix complement.

FIBRINOGEN• Also called clotting factor1

• Constitutes 4-6% of total protein

• Precipitated with 1/5 th saturation with ammonium sulphate

• Large asymmetric molecule

• Highly elongated with axial ratio of 20:1

• Imparts maximum viscosity to blood

• Synthesized in liver

• Made up of 6 polypeptide chains

• Chains are linked together by S-S linkages

• Amino terminal end is highly negative due to the presence of glutamic acid

• Negative charge contributes to its solubility in plasma and prevents aggregation due to electrostatic repulsions between the fibrinogen molecules.

GENETIC DEFICIENCIES OFPLASMA PROTEINS

• Analbuminaemia: Inherited disorder in which albumin is very low or completely absent. Defect is in the albumin synthesis. There is usually associated raised levels of plasma lipids and lipoproteins, which is probably secondary defect in lipid transport. All globulin fractions occur in increased concentration.

CONTINUED…• Bruton’s agammaglobulinaemia

• An inherited disorder, X-linked recessive traits, Differentiation of B-lymphocytes to plasma cells is defective leading to lack of plasma cells in circulating blood.

• There is absence of γ-globulins or γ-globulins level are very low, and lacks humoral immunity and susceptible to bacterial infections.

• Afibrinogenaemia: An inherited disorder characterized by genetic defect in fibrinogen formation. Inherited as a non-X-linked recessive trait characterized by absence of fibrinogen or very low level of fibrinogen. Blood clotting mechanism is hampered and there may be uncontrollable haemorrhages.

HYPOPROTIENURIA• Decease in total protein concentration

• Hemodilution- Both Albumin and globulins are decreased, A:G ratio remains same, as in water intoxication

• Hypoalbuminemia- low level of Albumin in plasma

• Causes-

• Nephrotic syndrome

• Protein losing enteropathy

• Severe liver diseases

• Mal nutrition or malabsorption

• Extensive skin burns

• Pregnancy

• Malignancy

THANK YOU FOY YOUR PATIENCE!

MADE BY:HUSSAN ARA

QARSHI UNIVERSITY