Heme synthesis and Path

Question 1

Porphyria path and presentation

Answer 1

….

Question 2

What cells produce heme

Answer 2

Erythrocytes and hepatocytes. hepatocytes in the microsomal cytochrome p450 system.

Question 3

How long do RBCs live

Answer 3

120 days (4 months)

Question 4

Where is heme made

Answer 4

In mitochondria and cytoplasm, when RBCs lose the mitochondria they can’t produce more heme.

Question 5

What is the first step of heme synthesis?

Answer 5

Succinyl CoA + Glycine to form aminolevulinic acid via ALA synthase (Aminolevulinic acid synthase) [

Question 6

What is the last step of Heme synthesis?

Answer 6

Combining Fe2+ with Protoporphyrin IX to produce heme with Ferrochelatase.

Question 7

Heme breakdown pathway

Answer 7

heme to biliverdin with heme oxygenase. Then to bilirubin, then in liver to bilirubin glucoronide via UDP-Glucuronyl transferase. Then urobilinogen via bacteria, secreted as either stercobilin or reabsorbed with a little bit going to form urobilin in urine.

Question 8

What effect does lead have

Answer 8

Lead inhibits ferrochelatase

Question 9

Most common porphyria

Answer 9

Porphyria cutanea tarda (PCT), defective uroporphyrinogen decarboxylase.