Heme Biochemistry (Part 2) Flashcards
Heme has a ____ ring with iron in the center
Porphyrin
Porphyrin structure
4, 5-membered rings
Iron is in what form in Heme?
Ferrous (Fe2+)
Where does Heme biosynthesis occur?
Liver and erythroid cells of bone marrow
Where do the 3 phases of Heme Biosynthesis occur?
- Mitochondria
- Cytosol
- Mitochondria
What are the starting products for Phase 1 of heme synthesis?
Glycine + Succinyl CoA
During Phase 1 of heme synthesis, what enzyme acts on Glycine + Succinyl CoA?
delta - Aminolevulinic Acid (ALA) Synthase
What is the end product of Phase 1 of heme synthesis?
delta - Aminolevulinic Acid (ALA)
What are the starting products for Phase 2 of heme synthesis?
ALA + ALA
For Phase 2 of heme synthesis, what enzyme combines ALA + ALA?
ALA Dehydratase
During Phase 2 of heme synthesis, ALA + ALA using ALA Dehydratase creates?
Porphobilinogen
During Phase 2 of heme synthesis, what is the end product?
Coproporphyrinogen III
During Phase 3 of heme synthesis, protoporphyrin is converted to?
Heme
What enzyme during Phase 3 of heme synthesis converts protoporphyrin to Heme?
Ferrochelatase
What does Ferrochelatase enzyme add to protoporphyrin?
Ferrous (Fe2+)
What does delta - aminolevulinic acid synthase require?
Vitamin B6
Where does Heme have negative feedback on its synthesis?
Delta - Aminolevulinic Acid Synthase
Lead poisoning inactivates which 2 enzymes in Heme synthesis?
ALA Dehydratase
Ferrochelatase
With lead poisoning, what substrates accumulate?
ALA Dehydratase – ALA accumulates
Ferrochelatase – Protoporphyrin IX
What does lead poisoning cause?
Anemia and impacts ATP synthesis
ALA accumulation is ____
Neurotoxic
Porphyrias
Defects in heme synthesis
What enzyme is deficient with Acute Intermittent Porphyria?
Porphobilinogen Deaminase
Acute Intermittent Porphyria symptoms
Hepatic - neurologic
What enzyme is deficient with Congenital Erythropoietic Porphyria?
Uroporphyrinogen III Cosynthase
Congenital Erythropoietic Porphyria symptoms
Erythropoietic - produces a red color of urine and teeth and skin photosensitivity
What enzyme is deficient with Porphyria Cutanea Tarda?
Uroporphyrinogen Decarboxylase
Porphyria Cutanea Tarda symptoms
Hepatoerythropoietic - neurologic and skin sensitivities
What enzyme is deficient with Variegate Porphyria?
Protoporphyrinogen Oxidase
Variegate Porphyria symptoms
Hepatic - neurologic
Heme is degraded to Biliverdin using what enzyme?
Heme oxygenase
Heme oxygenase takes Heme to Biliverdin using?
Oxygen
Heme oxygenase releases ____ & ____from heme
Iron (ferrous)
CO2
Biliverdin is converted to Bilirubin using what enzyme?
Biliverdin Reductase
Biliverdin Reductase requires _____ to convert Biliverdin to Bilirubin
NADPH
Bilirubin is sent into the blood stream and is bound to?
Albumin
In the liver, Bilirubin is combined with?
UDP - Glucuronate
Bilirubin is combined with UDP-Glucuronate using what enzyme?
UDP - GlucuronylTransferase
What is the rate limiting step of Heme degradation?
UDP - GlucuronylTransferase combining UDP-Glucuronate and Bilirubin to form Bilirubin Diglucuronide
Bilirubin + UDP - Glucurornate =
Bilirubin Diglucuronide
Bilirubin Diglucuronide is then sent to?
Gallbladder
Once Bilirubin Diglucuronide is in the intestines, it is converted to?
Urobilinogen
If urobilinogen is sent to the kidneys, it becomes?
Urobilin
Urobilin causes?
Urine to be yellow
If urobilinogen remains in the intestines, it becomes?
Stercobilin
Stercobilin causes?
Red, brown color to feces
Jaundice means
Hyperbiliurbinemia
What are the 3 locations of disorders for jaundice?
Pre-hepatic
Intra-hepatic
Post-hepatic
Pre-hepatic jaundice is increased?
UNconjugated Bilirubin
What are the 2 common diseases with intra-hepatic jaundice disorders?
Criggler-najjar syndrome
Gilbert syndrome
What enzyme is usually absent or deficient with intra-hepatic disorders?
UDP - GlucuronylTransferase
Post-hepatic jaundice is increased?
CONJUGATED Bilirubin
What symptoms will post-hepatic jaundice patients have?
DARK urine and pale stool
Hepatitis: increased unconjugated or conjugated bilirubin in the blood?
BOTH