Heme Synthesis Facts
Key rate-limiting step:
Glycine + sucinyl CoA forming d-amnolevulinic acid
ALA synthase is inhibited by heme thus:
Other enzymes inhibited by heme:
As heme increases d-amnolevulinic acid production decreases
ALA dehydratase =
Decreased porphobilinogen
Porophobilinogen  deaminase =
Decreased Uroporphyrinogen III
Ferrochelatase =
Other enzymes inhibited by heme and protoporhyrin IX:
Decreased heme