Flashcards in Heme Synthesis: Porphyrias Deck (15):
What are the major tissues for heme synthesis?
Besides hemoglobin and myoglobin, heme can act as a prosthetic group of what enzymes?
Cytochromes of ETC
The four pyrrole rings of Heme are linked via what?
Which amino acid is used for heme synthesis?
In regards to heme synthesis, succinyl CoA and glycine are used to form what?
Gamma-aminolevulinic acid (ALA)
What are the two isoforms of ALA? Where are they found? What regulates them?
ALA synthase 1 - liver
ALA synthase 2 - RBC
ALA 1 is inhibited by heme
ALA 2 is inhibited by low intracellular iron
Both require PLP, which can be inhibited by Isoniazid
Regarding heme syntheis, 2 ALA's form what in cytosol?
What is used to form the linear hydroxymethylbilane (HMB)
Defiencies of ALAS2 leads to what disease?
Sideroblasticic anemia (x-linked)
The gene for ALAS2 is on which chromosome?
Which enzyme combines to ALA to form porphobilinogen? What inhibits this enzyme?
ALA dehydrate (aka Porphobilinogen synthase)
Inhibited by: Lead
Note: Enzyme requires Zinc as cofactor
Which reaction does the PBG deaminase, or also known as HMB synthase, catalyze? What disease is related to the deficiency of this enzyme?
Combines 4 porphobilinogen to form hydroxymethylbilane.
Disease: Acute Intermittent Porphoria (NOT photosensitive)
Which of the diseases are related to severe photo-sensitivity in heme synthesis? Which enzyme is deficient?
1) Congenital Erythropoietic porphoria
2) Porphyria Cutanea Tarda
3) Erythropoietic Protophyria
What is the treatment for porphyrias?
-Intravenous injection of glucose