3. Iron homeostasis Flashcards
What is Fenton reaction?
Iron-dependent generation of reactive oxygen spieces
What is the equation for Fenton reaction?
Absorbtion and reduction of Fe3+ in the cells of the duodenum
Where is iron storage?
ferritin
Absorbtion of iron in hepatocytes
Iron metabolism in the cell
Regulation of intracellular iron with ___ (enzyme?)
IRP-1 (cytoplasmic aconitase)
Regulation of intracellular iron with IRP-1 (cytoplasmic aconitase)
-> What happen when there is low intracellular iron concentration?
What happen when there is a high intracellular iron concentration?
Systemic iron availability is regulated by ____
hepcidin
Systemic iron availability is regulated by hepcidin
-> What happen if there is low serum iron?
Hepcidin expression low, ferroportin is not degraded, iron is exported into the circulation from gut, liver, macrophages
Systemic iron availability is regulated by hepcidin
-> What happen if there is high serum iron?
Tf-Fe3+ induces expression of hepcidin, iron export is decreased through ferroportin from macrophages, liver.
Inflammation increases hepcidin synthesis, erythropoesis and hypoxia decreases it.
Cause of problems in iron homeostasis?
Alterations of systemic iron homeostasis caused by imbalances of the Hepcidin/Ferroportin regulatory system
Structure of hemes
They are tetrapyrroles, of which two types, heme b and heme c, predominate (Figure 31–5).
Where does heme synthesis occur?
mitochondria and cytosol
Where does heme synthesis occur?
mitochondria and cytosol
How is heme produced?
Mito:
Gly+SuccCoA 5-ALA
Cytosol:
8 x 5-ALA –> coproporphyrinogen III
Mito: ferrochelatase - hem
Steps and cellular location of the reactions in the biosynthesis from porphobilinogen of the indicated porphyrin derivatives, notably heme.
-> Identify
- Coproporphyrinogen III
- Ferrochelatase
What is the Regulated reaction in the synthesis of a porphyrins: ALAS (Mitochondria)?
ALAS-1 izoenzym in the liver is regulated by ___
heme
Hem synthesis in erythroblasts – ALAS-2 is regulated by ___ and ___
eythropoietin and Fe2+
What is Porphyria cutanea tarda?
Uroporphomethene: a (Fe2+ dependent) partially oxidized uroporphyrinogen, acts as an inhibitor of uroporphyrinogen decarboxylase
What is Congenital erythropoietic porphyrin?
Deff: uroporphyrinogen III synthase
CATABOLISM OF HEME PRODUCES ___
BILIRUBIN
Hem degradation with hem-oxygenases: results in ____
Bilirubin and – CO – Fe2+ .
is bilirubin soluble in blood?
NO!
Why is Bilirubin a good antioxidant?
Bilirubin – a lipophyl antioxidant – inhibits peroxidation of membrane lipids
