Serum Proteins 1 Flashcards
what is centrifugation
Blood separation into plasma and formed elements (erythrocytes, leukocytes and platelets) found floating in the aqueous plasma. The different elements separate as they are different densities.
describe separation of serum proteins
Separation is performed by serum protein electrophoresis (SPEP)
Gel or paper electrophoresis will separate the proteins within the serum according to their size and charge
who can changes in electrophoresis profile indicate a medical condition
Serum proteins are made in the liver so problems with blood proteins could indicate liver problems. If proteins are excreted in urine, then there may be a problem with the kidneys.
Increased gamma globulins indicate infection, lymphoma, rheumatoid arthritis.
what/how would Hepatic Cirrhosis change in profile of SPEP
- liver function is sufficiently diminished
- protein synthesizing capacity is compromised
- This leads to decreased concentrations of albumin and alpha and beta globulins shown in the SPEP
- An additional common finding is beta-gamma bridging due to increased IgA.
what/how would Nephrotic Syndrome change in profile of SPEP
- Renal disease causes large protein loss
- Smaller proteins may be excreted e.g. albumin but larger ones e.g. alpha-2-macroglobulin do not
- General hepatic protein synthesis to combat loss makes alpha-2- macroglobulin accumulate.
what are properties of serum albumin?
- A single polypeptide 585 amino acids long
- Molecular weight is 66,248KDa
- A strong negative charge of -17 (this charge allows it to carry other things around the blood stream)
describe production of serum albumin
- It is not stored in the body, therefore there are no reserves
- Produced by the Liver (9-12g each day) Production can only increase by 2 or 3 fold (liver has a certain capacity)
- The rate of production is controlled by changes in the colloid osmotic pressure and osmolality. It is not catabolised (broken down) in starvation
- T1/2 is 16-18 hours
- Intravascular concentration of ~40g/L
- Also exists in the extravascular (interstitial) space
how can serum albumin be affected in illness
Serum albumin is the most abundant serum protein and therefore a good indicator of health.
Levels decrease with malnutrition, liver and kidney disease, low levels of physical activity, heavy smoking, loss of strength and age.
what are 4 functions of serum albumin
• An Important intra and extravascular protein
• It contributes strongly to colloid osmotic pressure
• Main functions are binding and transport
o Osmotic pressure
o Free radical scavenging
o Inhibition of platelet function
o Antithrombotic effects
How (and what) does serum albumin transport?
This is a highly water soluble protein (due to its charge)
It therefore ‘carries’ other molecules that are poorly water soluble e.g. hormones, free fatty acids, drugs, toxins, bilirubin
describe osmoregulation in relation to serum albumin
Serum albumin is a major protein in plasma and maintains water balance to prevent oedema.
In severe protein deficiency, the body begins to break down its own muscle and also blood proteins. This reduces the osmotic pressure of blood and causes outflow to be significantly greater than inflow, resulting in oedema, which is the accumulation of tissue fluid.
what is Hypoalbinaemia and what causes it
Abnormally low levels of Albumin
Can be caused by overhydration (rare)
The most common cause is decreased synthesis (malnutrition or liver disease)
what are 4 other functions of serum albumin (not the main ones which are an Important intra and extravascular protein, contributes strongly to colloid osmotic pressure, main functions are binding and transport)
- Free radicals scavenging – via the free sulfhydryl groups R-SH (thiols) on the albumin binding to reactive nitrogen and oxygen species.
- Acid Base Balance
- Anti-coagulant effect
- Vascular permeability
how does serum albumin affect free radicals scavenging
via the free sulfhydryl groups R-SH (thiols) on the albumin binding to reactive nitrogen and oxygen species.
Free radicals are atoms or groups of atoms with an odd (unpaired) number of electrons and can be formed when oxygen interacts with certain molecules.
Once formed these highly reactive radicals can react with and damage important cellular components such as DNA, or the cell membrane.
e.g. a common reactive form of oxygen that is formed when molecular oxygen gains a single electron generating ‘Superoxide’ radicals which can attack susceptible biologic targets, including lipids, proteins, and nucleic acids.
how does serum albumin affect acid base balance
highly negatively charged, the concentration of cations and anions in plasma should be equal.
how does serum albumin affect vascular permeability
It is possible that albumin may have a role in limiting the leakage
what is the main type of alpha 1 globulins
α1–antitrypsin
what is the function of α1–antitrypsin
to limit damage of connective tissue in the lung caused by proteases.
There is usually more α1– antitrypsin than elastase.
Elastase breaks down elastin which is connective tissue that gives the lungs stretch- antitrypsin stops elastase breaking down too much elastin.
a1-antitrypsin has a flexible loop that acts as “bait” for Neutrophil elastase.
how does smoking affect α1-antitrypsin
Cigarette smoke can lead to oxidation of methionine 358 of α1-antitrypsin, a residue essential for binding elastase
Loss of elasticity in lung makes breathing difficult as air sacs and capilliaries are broken.
what is haptoglobin
a protein (synthesized in liver)
what is the function of haptoglobin
Binds free haemoglobin and sequesters the iron within it allowing its removal by the reticuloendothelial system
Allows degradative enzymes to get near free haemglobin, prevents iron loss via kidneys and protects kidneys from oxidative damage.
Haemolysis is premature destruction of red blood cells that releases haemoglobin into plasma. A drop in Haptoglobin concentration is diagnostic for haemolysis
what is the clinical significance of heptoglobin (3 things)
Mutations in gene or regulatory regions of protein = hypohaptoglobinemia - linked to diabetic nephropathy, Crohn’s disease and increased susceptibility to idiopathic Parkinson’s disease.
Sequestration of iron by Haptoglobin reduces incidence of iron utilising bacteria which thrive during haemolysis.
Most inflammatory processes (infection, extreme stress, burns, extreme allergy, trauma) increase Haptoglobin concentration in serum.
what would the following indicate (HINT: anaemia):
- Haptoglobin decreased and reticulocyte increased (RBC decreased)
- Haptoglobin normal and reticulocyte increased
- Haptoglobin normal and reticulocytes normal
- Haptoglobin levels low and there are no signs of haemolytic anaemia
- likely to be haemolytic anaemia.
- this may indicate that RBC destruction is occurring in the in spleen or liver i.e. drug induced haemolysis. As heptaglobin has not altered
- any anaemia observed is not likely to be due to RBC breakdown (possibly aplastic anaemia – due to a defect in the ability of bone marrow to replenish blood cells).
- likely to be due to the liver not producing enough haptoglobin.
Copper is an essential cofactor for many enzymes with within the body - how is it redistributed throughout the body
After ingestion, it is absorbed from the small intestine into the bloodstream Where it is transported to the liver bound to transport proteins.
This allows the copper to be re-distributed throughout the body
what are the functions of copper
- Involved in synthesis of melanin in the skin
- Generation of cellular energy (ATP) and collagen
- Involved in the production of iron to useable (ferric) form, in the brain
- It is involved in neurotransmitter proudcytion and myelin (nerve insulator) production
- Needed for maintenance of white blood cells, important for blood coagulation
what can happen if there is excess copper
leads to neurological, psychiatric, and liver disease
what does the liver produce when there is inflammation
heptoglobin, C£, C-reactive protein, serum amyloid A, fibrinogen
what is ceruloplasmin and what does it do?
The plasma Copper (Cu2+) storage /transport protein.
It retains 95% of copper in plasma and binds 6 copper atoms per molecule. (Albumin binds the other 5%: less tightly than ceruloplasmin)
Ceruloplasmin has enzymatic activity that is triggered by copper. What does it then do?
It acts as a copper dependent oxidase turning Ferrous iron Fe2+ into Ferric iron Fe3+, assisting in the transport of iron by transferrin which only binds ferric iron
what is α 2-macroglobulin
A family of glycoproteins with anti-protease activity with “bait” region, activated on protease activity.
what is the function of α 2-macroglobulin and how does it do this?
Has ability to inactivate a massive range of proteases from all classes (including Plasmin which degrades fibrin clots).
Contains a receptor binding domain that binds to α2-m receptor to enable clearance of protease-a2-m complex.
what conditions would cause α 2-macroglobulin to be elevated and decreased?
Elevated in diagnosis of Nephrotic syndrome, diabetes, burns. Deficiency in COPD.
what is the acute phase response
The acute phase response is a Nonspecific response to tissue injury, toxic challenge or infection.
what happens to the body during acute phase response
• Inflammatory cells secrete cytokines (IL’s, TNF)
liver responds by synthesising number of specific proteins.
• Others proteins are downregulated.
• Increases in C-reactive protein and complement will contain and eliminate infection.
• Increased clotting factors which aid and prevent excess blood loss.
• Increased protease inhibitors which will prevent the spread of tissue necrosis.
What is evidence of the acute phase response from the SPEP?
There is a marked increase in the levels of a1+2 globulins: increased a1-antitrypsin, ceruloplasmin, haptoglobin and a2-macroglobulin
what is the c-reactive protein
C-reactive protein(pentraxin) is major component of the acute phase response.
It is has 5 subunits,
with protease activity
It is extremely thermostable
what does the c-reactive protein do, and how?
It binds to phosphorylcholine on microbes, aiding phagocytosis via the C-reactive protein receptor.
It assists in complement binding.
Each subunit has two faces, one with a pocket that binds Pc (calcium dependent), the other binds to receptor and can activate C1q, part of the complement system.
what is monomeric C- reactive protein a biomarker for (what does it indicate)
heart disease
what conditions does erythrocyte sedimentation rate (ESR) increase?
ESR is increased in any condition causing an increase in fibrinogen (any cause of tissue breakdown) or globulins.
ESR is increased in all conditions where there is tissue breakdown or where there is entry of foreign proteins in the blood, except for localized mild infections
what is the Rouleaux formation? how and why does it change in chronic infections?
when RBC stack together in long chains therefore sediment more readily
The changed levels of plasma proteins such as fibrinogen and globulins which accompany most of the acute and chronic infections tend to increase rouleaux formation
ESR is useful to check the progress of the disease - how?
If the patient is improving the ESR tends to fall.
If the patient’s condition is getting worse the ESR tends to rise.
The changes of ESR are, however, not diagnostic of any specific disease.
Serum proteins can be separated using electrophoresis. - what can this be used for?
This represents a diagnostic tool as predictable changes occur during disease.
what are the main functions of serum albumin
transport of small hydrophobic molecules (structure) and osmoregulation (abundance)
describe how alpha globulins are grouped
Alpha-globulins are split into a1 and a2 and comprised of proteins whose structure enables them to inhibit proteases or bind free metal ions.
what is the acute phase response
The acute phase response is a non-specific reaction in which the body up/down regulates some functional proteins.
how is acute phase response measured
C reactive protein is a multifunctional protein that is expressed in the acute phase response. ESR also used to monitor acute phase response.
why can some enzymes be used in diagnosis and disease monitoring
Some enzymes only exist in serum following the onset of a disease, these can be used for diagnosis and monitoring of disease progression.
