DEFINITION
Serum Transferrin is a beta-globulin that transports iron in the plasma. It is a glycoprotein that binds iron very tightly but reversibly. When not bound to iron, it is known as apotransferrin. Although iron bound to transferrin is less than 0.1% (4 mg) of the total body iron, it is the most important iron pool, with the highest rate of turnover (25 mg/24 h). This turnover accounts for most of the daily internal iron exchange between body tissues.
CHEMICAL STRUCTURE AND IMAGES
When relevant for the function
Transferrin has a molecular weight of around 80 kiloDaltons and contains 2 specific high-affinity Fe(III) binding sites. The affinity of transferrin for Fe(III) is extremely high (1023 M-1 at pH 7.4) but decreases progressively with decreasing pH below neutrality.
- Secondary structure
- Tertiary structure
- Quaternary structure
Transferrin is a glycoprotein Define better ???
Protein Aminoacids Percentage
The Protein Aminoacids Percentage gives useful information on the local environment and the metabolic status of the cell (starvation, lack of essential AA, hypoxia)
SYNTHESIS AND TURNOVER
Albumin and transferrin synthesis during development in the rat 1974
Intracellular Aspects of Transferrin Synthesis and Secretion in the Rat 1971
Albumin and transferrin synthesis are increased in H4 cells by serum from analbuminemic or nephrotic rats 1994
Stimulatory effect of 1,25-dihydroxyvitamin D3 on transferrin synthesis in primary cultures of adult rat hepatocytes. 1990
mRNA synthesis
protein synthesis
post-translational modifications
degradation
CELLULAR FUNCTIONS
Cellular localization,
- Transferrin is a serum protein, synthesized mainly in the liver: but other sources such as the brain also produce this molecule .
Biological function
- The main role of transferrin is to deliver iron from absorption centres in the duodenum and red blood cell macrophages to all tissues. Predominantly, transferrin plays a key role where erythropoiesis and active cell division occur.
- Transferrin Iron affinity is modulated by bicarbonate
elevated lactic acid but not carbonic acid leads to proton-induced dissociation of carbonate bonds in the transferrin-iron complex
Transferrin carries also Mn++
REGULATION
DIAGNOSTIC USE
High serum transferrin levels are found in patient with iron deficiency
Low levels are found in those with iron overload, hepatopathy and malnutrition.
Serum transferrin concentration = 1,6-3,6 g/l
Transferrin half-life = 8-10 days
Transferrin saturation = 20-45 %
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Transferrin metabolism in alcoholic liver disease. 1985
Transferrin Iron saturation is reduced in pregnancy
Normal pregnancy is characterized by a state of decreased insulin sensitivity, as well as accelerated lipolysis and ketogenesis. The concentration of serum ketones has been estimated to be two to four times greater than in the nonpregnant state.1, 5 In addition, pregnant women have a respiratory alkalosis, lowering the serum bicarbonate concentration, thus reducing the capacity to buffer hydrogen ions.
Normoglycemic diabetic ketoacidosis in pregnancy 2008
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Iron transferrin regulates hepcidin synthesis in primary hepatocyte culture through hemojuvelin and BMP2/4 2007
Repression of {alpha}-Fetoprotein Gene Expression under Hypoxic Conditions in Human Hepatoma Cells 2002
Melanoferrin
Site
Transferrin receptor mediated Iron uptake
Figure 3. Cellular uptake of iron through the Tf system via receptor-mediated endocytosis.
Transferrin: structure, function and potential therapeutic actions.
Transferrin/transferrin receptor-mediated drug delivery.
The transferrin receptor part II: targeted delivery of therapeutic agents into cancer cells.
Transferrin and transferrin receptors
Transferrin
Bella Tesina 2008
Graphs show intracellular pH as determined by 31P magnetic resonance spectroscopy and estimated intracellular bicarbonate levels during ischemia and reperfusion (mean values±SEM). Zero time indicates the start of reperfusion. Time scale is compressed after 60 minutes to emphasize early transients. Groups are saline vehicle, n=8; free deferoxamine (DFO), n=8; hydroxyethyl starch vehicle (HES), n=6; and hydroxyethyl starch–conjugated deferoxamine (HES-DFO), n=5. *P<.05 from respective vehicle group.