Heme Synthesis & Hemoglobin Flashcards
1
Q
Which steps of heme synthesis take place in the mitochondria and which take place in the cytosol??
A
1st & last 3 steps occur in the mitochondria
Intermediate steps occur in the cytosol
2
Q
Where do all the carbon and nitrogen atoms of porphyrin molecules come from?
A
Succinyl CoA and glycine
3
Q
What catalyzes the committed step in heme biosynthesis?
A
ALAS
4
Q
What are the two isoforms of ALAS?
A
ALAS1 = liver isoform ALAS2 = erythroid/reticulocyte isoform
5
Q
Which isoform of ALAS is regulated by a negative feedback mechanism of heme/hemin?
A
ALAS1 (liver isoform)
6
Q
Which step in heme biosynthesis does lead inhibit? What happens with lead poisoning?
A
Lead can displace Zinc, inhibiting ALA dehydratase
This leads to an increase in ALA –> neuro effects, toxic to brain
