Lecture 1 Proteins

Lecture 1: Plasmatic proteins

2009-2010

Content of lecture 1:

1. Structure, function and production of plasmatic proteins.2. Quantitative changes of plasmatic proteins (hypo and

hyperproteinemias)3. Electrophoretic separation of plasmatic proteins. Disproteinemias.4. Disproteinemia in acute phase reaction5. Disproteinemia in chronic inflammation6. Disproteinemia in nephrotic syndrome7. Disproteinemia in exudative enteropathy8. Disproteinemia in monoclonal gammopahties9. Disproteinemia in hypo gamma globulinaemia10. Deficiency of specific proteins: alfa1 antitrypsine, antithrombin III

1.1. Structure, function and production of plasmatic proteins

Proteins are made of aminoacids, bound Proteins are made of aminoacids, bound together by peptide bondstogether by peptide bonds::

• primary structure (primary structure (= secvenţa reziduurilor = secvenţa reziduurilor de aminoacizi din lanţul polipeptidicde aminoacizi din lanţul polipeptidic),),

• secondary structure (alpha-helix, beta – secondary structure (alpha-helix, beta – sheet, a local conformation stabilized by sheet, a local conformation stabilized by hydrogen bonds),hydrogen bonds),

• Tertiary structure (the overall shape of a Tertiary structure (the overall shape of a single protein molecule)single protein molecule)

• Quaternary structure (the structure Quaternary structure (the structure formed by several protein molecules formed by several protein molecules (polypeptide chains), usually called protein (polypeptide chains), usually called protein subunits).subunits).

1.2. Cellular localization and Synthesis of proteins

1.3. Protein in nutrition

Most microorganisms and plants can biosynthesize all 20 standard amino acids,

Animals (including humans) must obtain some of the amino acids from the diet.

The amino acids that an organism cannot synthesize on its own are referred to as essential amino acids.

1.4. Metabolism of proteins

Catabolism of proteins by: Denaturation (acid) Hydrolysis (proteases)

Some ingested amino acids are used for protein biosynthesis, while others are converted to glucose through gluconeogenesis, or fed into the citric acid cycle. This use of protein as a fuel is particularly important under starvation conditions as it allows the body's own proteins to be used to support life, particularly those found in muscle

2. Quantitative changes of plasmatic proteins (hypo and hyperproteinemias)

Hypoproteinemia is mainly associated with hypoalbuminemia Hyperproteinemia is mainly associated with hyperglobulinemia

In the past were used tests to identify which fraction is increased (Tymol test, Kunkel test, ZnSO4 test) – these tests were orientative, not precise.

Electrophoretic separation of proteins is used to identify a syndrome, not to indicate the cause.

PROTEINE TOTALE SERICE. PROTEINOGRAMAPRINCIPALELE PROTEINE PLASMATICE Peste 90 de proteine au fost izolate şi purificate din sânge. Separarea proteinelor ( în funcţie de sarcină, mărime), pe un suport solid, într-un câmp electric = proteinogramă.

FRACŢIUNEA % G/100ML1 Albumina 52 – 60 3,5 – 5,52 α1 globuline 3 – 5 0,25 – 0,353 α 2 globuline 8 – 10 0,5 – 0,754 β globuline 12 – 14 0,8 – 1,055 γ globuline 16 - 20 1,1 – 1,5

Electrophoretic separation of plasmatic proteins.

Disproteinemias

A change in Albumin/ Globulin ratio. Ratio can be modified even at a normal protein

concentration! Classification of disproteinemia:

With normal TP (total protein) concentration Acute phase reaction, Chronic inflammation

With decreased TP concentration Nephrotic syndrome, liver cyrrhosis, exudative

enteropathy With increased TP concentration

Multiple myeloma, Waldenström disease, Light chains disease

Disproteinemia in acute phase reaction

Change in Acute-Phase Reactants After a Moderate Inflammatory Stimulus

Gabay C, Kushner I. N Engl J Med. 1999;340:448-454.

Ch

ang

e in

Pla

sma

Co

nce

ntr

atio

n (

%)

30,100

30,000

700

600

500

400

300

200

100

0

0 7 14 21Time After Inflammatory Stimulus (days)

Serum amyloid A

C-reactive protein

Haptoglobin

Fibrinogen

C3

Albumin

Transferrin

Disproteinemia in chronic inflammation

Disproteinemia in nephrotic syndrome, liver cyrrhosis, exudative enteropathy

Disproteinemia in monoclonal gammopahties

Disproteinemia in hypo gamma globulinaemia

Hypogammaglobulinemia is a disorder that is caused by a lack of B-lymphocytes and a resulting low level of immunglobulins (antibodies) in the blood

The most common congenital abnormalities of B lymphocyte production include: Hypogammaglobulinemia (Common Variable

Immunodeficiency) Ig A Deficiency X-linked Agammaglobulinemia (Bruton Disease) Transient hypogammaglobulinemia of infancy

Disproteinemia in hypo gamma globulinaemia

Chronic infections: Giardia lamblia, bronchitis and sinusitis. These infections respond to antibiotics but recur upon discontinuation of the medications.

Chronic diarrhoea (including protozoan and parasitic infections). Chronic swelling of the lymph glands. Enlarged spleen. Atrophic gastritis with pernicious anemia. Nodular lymphoid hyperplasia of the intestine. This finding can be

mistaken for intestinal lymphoma. Increased intestinal permeability (i.e. leaky gut). Villous atrophy in the small intestine, which can resemble coeliac

disease and cause diarrhoea and malabsorption. Increased incidence of inflammatory bowel disease. Polyarthritis, or joint pain, spread across most joints, but specifically

fingers, wrists, elbows, toes, ankles and knees. Fatigue. Malabsorption. Weight loss.

How is it diagnosed?

Some tests that indicate hypogammaglobulinemia include:

Low serum immunoglobulins and B lymphocytes

Missing specific antibodies to any vaccines the child has received

Absence of antibodies to A and B blood group antigens

Deficiency of specific proteins: alfa1 antitrypsine

is a genetic disorder caused by defective production of alpha 1-antitrypsin (A1AT), leading to decreased A1AT activity in the blood and lungs, and deposition of excessive abnormal A1AT protein in liver cells.

There are several forms and degrees of deficiency. Severe A1A deficiency causes panacinar emphysema and/or COPD in adult life in many people with the condition (especially if they are exposed to cigarette smoke), as well as various liver diseases in a minority of children and adults, and occasionally more unusual problems.

It is treated by avoidance of damaging inhalants, by intravenous infusions of the A1AT protein, by transplantation of the liver or lungs, and by a variety of other measures, but it usually produces some degree of disability and reduced life expectancy

Deficiency of specific proteins: antithrombin III

Antithrombin III deficiency is a rare hereditary disorder that generally comes to light when a patient suffers recurrent venous thrombosis and pulmonary embolism. Inheritance is usually autosomal dominant, though a few recessive cases have been noted.

In renal failure, especially nephrotic syndrome, antithrombin is lost in the urine, leading to a higher activity of Factor II and Factor X and in increased tendency to thrombosis.

DETERMINATION METHODS FOR PROTEINSDETERMINATION METHODS FOR PROTEINS

IMMUNOFLUORESCENCEIMMUNOFLUORESCENCE – (A– (ABB antinuclear), antinuclear), Ag tisularAg tisular

LATEX ALATEX AGGGLUTINAGLUTINATIONTION – CRP, FR, Ac – CRP, FR, Ac antiDNantiDNAA

ELISA, RIAELISA, RIA – hormon – hormonss IMIMMMUNODIFUUNODIFUSIONSION –– for for identifica identification oftion of Ag Ag

oror A Abb ELECTROELECTROPHORESISPHORESIS - proteinogram - proteinogram COLORIMETRCOLORIMETRYY – – total total protein, albuminprotein, albumin NENEPHPHELOMETRELOMETRYY – – Fibrinogen, ImunglobulinFibrinogen, Imunglobulinss