BC2001 plasma proteins

Globular proteins

Amino acids fold into shapes that resemble spheres

Polar group on surface

This folding increases solubility

Fibrous protein

Mainly insoluble structural proteins

Globular proteins

Hemoglobin, myoglobin, ß-globulins, y-globulins, enzymes

Hemoglobin

Oxygen transport function

Myoglobin

Oxygen storage supply in heart and muscle

y-globulins (immunoglobulins)

Immune function

Enzymes

Catalysis of biochemical reactions

Hemoglobin structure

2 alpha and 2 beta chains

Held together by non covalent interactions

Each chain is a subunit with heme group in centre that carries oxygen

Hb molecule

Contains 4 heme groups and carries 4 molecules of oxygeb

HbA 1c

glycosylated hemoglobin

High in patients with diabetes mellitus

Abnormal Hbs

Unable to transport O2

Carboxy Hb

When CO combines with Hb to form HbCO, CO replaces O2, binds 200x tighter

Met Hb

Contains oxidised Fe3+ that cannot carry oxygen

Sulf Hb

Forms due to high sulfur levels in blood (irreversible)

Disorders of Hemoglobin

Synthesis of structurally abnormal Hb

Synthesis of insufficient quantities of normal Hb

Sickle cell disease

Caused by single mutation in ß-globulin in gene

Glutamic acid in pos 6 replaced by valine

Albumin

Most abundant protein produced in liver

Transports hormones, fatty acids

Prevents blood leaking from capillary

Half life - 20 days

Soluble and monumeric

Albumin functions

Maintains oncotic pressure

Transports hormones, fatty acids, many drugs, competitively binds Calcium ions, buffers pH

Albumin synthesis

Pro-albumin -> signal peptidase -> signal peptide + proalbumin -> furin -> hexapeptide + albumin

Albumin shape

Ellipsoidal shape, does not increase viscosity of plasma X fibrinogen

Hypo-albuminemia

Low level of albumin in the blood

Caused by liver disease, excess excretion by kidneys,

hyper albuminemia caused by

Chronic dehydration

Vit A deficiency

High protein diets

Albumin analysis

1ml albumin added to bromcresol (green)

Acidic medium green transforms to blue/green, intensity associated w/ albumin concentration

Further measured by spectrophotometry

Acute phase reactants

-Factors whose serum concentrations change significantly in response to inflammation; produced by the liver in both acute and chronic inflammatory states.

-Notably induced by IL-6.

C reactive protein

1000x increase during inflammation

Positive ARPs (increase during inflammation)

fibrinogen, haptoglobin, serum amyloid A, A-antitrypsin

Globulin types

alpha (a1 and a2), beta (b1 and b2), gamma (y)

Globulin is made

In liver or by immune system

Globulin function

antibodies and lipid transport, can bind haemoglobin and transport metals in blood

Separating globulin subtypes

By serum protein electrophoresis, based on electrophoretic mobility and sedimentation coefficient

a1-globulin proteins

a1-fetoprotein and a1-antitrypsin

a2-globulin

a2-fetoprotein and haptoglobin

B-globulin

Transferrin and ceruloplasmin

y-globulins (gamma)

Immunoglobulins IgA, IgM, IgG. IgE

Under disease conditions, plasma protein..

Levels may change from normal range

Transferrin

Binds free iron in serum for transport, 1/3 saturated with iron

Decreased levels of transferrin indicate

Liver disease, nephrosis

Increased levels of transferrin indicate

Iron deficiency

Are free iron ions toxic?

Yes, catalyse formation of toxic hydroxyl radical (•OH) (Fenton reaction)

Immunoglobulins

Antibodies produced by B cells in response to antigen stimulation

Structure of immunoglobulins

4 polypeptide chains

2 heavy and 2 light chains linked by disulfide bridge

Light chains contain constant and variable region

Plasma enzymes

Cholinesterase, plasma superoxide dismutase, lecithin-cholesterol acyltransferase