Serum Proteins & Associated Disorders Flashcards
Albumin
55‐60% total protein in serum
70-80% total osmotic pressure
anionic at pH 7.4
synthesized by liver
functions:
maintenance of colloidal osmotic pressure
carrier or transport protein
serum albumin levels in an indicator of:
- nutritional status
- liver synthetic function
- integrity of glomerular BM
presence of albumin in urine
-implies damage to BM
glycosylated in blood at high serum glucose levels
Binds:
- Cations in blood (binds Ca2+) increase in pH = higher Ca2+ binding
- Free fatty acids (noncovalently in hydrophobic pockets)
- Thyroixine
- Bilirubin (noncovalently in hydrophobic pockets)
- Transport to liver for conjugation
Hypoalbunimeia
decreased syntehsis of albumin
- low protein diet (Kwashikor)
- chronic liver disease (cirrhosis)
increased loss of albumin
- severe burns
- loss of albumin in urine (nephrotic syndrome)
a1 antitrypsin
90% of a1 globulins
inhibitory protein agianst neutrophil elastase in alveoli
synthesized in liver, n-glycosylated > blood > lung alveoli
alpha1 antitrypsin deficiency
elastase destroys alveoli of lung,
- resulting in emphysema and COPD
- neutrophil elastase is not inactivated
- patients are also at a higher risk of developing cirrhosis and liver failure
Smoking
- increased neutrophil activity (increased elastase in lungs)
- cigarette smoke oxidized methionine residue in a1-antitrypsin (essential for binding to elastase)
alpha1 Fetoprotein (AFP)
AFP is abundant in fetal plasma‐
similar function to albumin in fetal
life
low in healthy adults
tumor marker for hepatocellular, ovarian, testicular cancers
high maternal serum AFP: neural
tube defects
low maternal serum AFP: down
syndrome
Transcortin
alpha 1 globulin
main transport protein of cortisol
binds 75% of steroid hormone
Retinol binding protein (RBP)
alpha 1 globulin
transports retinol (vitamin A) in blood from liver > peripheral tissues retinyl esters stored in liver
alpha 2 macroglobulin
alpha 2 globulin
largest serum proteins
protease inhibitor
binds to and inactivates proteases like plasmin, thrombin
elevated in nephrotic syndrome
Ceruloplasmin
alpha 2 globulin
synthesized and secreted by the
liver
binds copper and has ferroxidase activity
changes ferrous iron (2+) > ferric iron (3+) (can now be bound to transferrin in blood)
low ceruloplasmin levels
- Wilson’s disease: copper overload disorder
Haptoglobin
binds free hemoglobin
Hb-haptoglobin complex taken up itno macrophages
Haptoglobin‐Hb complex cannot be excreted by the kidneys‐‐prevents loss of iron and globin from body in cases of hemolysis
low serum haptoglobin‐acute
hemolysis
used to monitor hemolytic anemia
Wilson’s disease
Low ceruloplasmin levels
deficiency in copper-transporting ATPase (ATP7B)
Apoceruloplasmin released from liver and degraded in serum (5 hr half life insetead of 5.5 days for ceruloplasmin)
Copper accumulation
-liver, brain, eyes, “Kayser-Fleischer rings”, kidney
Hemopexin
beta globulin
binds to free heme in circulation prevents loss of iron by the kidneys
heme-hemopexin taken up into hepatocytes
hemopexin prevents:
- heme mediated oxidative damage to plasma membrane
- heme intercalcation into lipid membranes lead to membrane damage (leaks due to lipid peroxides)
- heme usage as important source of iron for pathogenic microorganisms
Transferrin
beta globulin
transports iron between intestine, liver, bone marrow, and spleen
each transferrin can bind two Fe3+atoms, normally 1/3 of the binding sites are saturated
iron deficiency: low transferrin saturation
iron overload: high serum iron and high transferrin saturation
B-lipoprotein
beta globulin
have only apo B-100 (postive charge)
sperated in B-globulin fraction by electrophoreisis
Acute Phase Proteins
C‐reactive protein
deprive microbes of iron and inhibit growth
ceruloplasmin
haptoglobin
cytokines released during inflammation stimulate hepatic synthesis of these proteins
CRP levels are used to measure the progress of an inflammatory reaction
