Porphyrins and Nucleotide synthesis

Condensation of glycine and succinyl CoA

Porphyrin Synthesis

1. two d-aminolevulinate condense to porphobilinogen

2. four porphobilinogen condense to tetrapyrrole

3. cyclized to uroporphyrinogen III

Porphyrias

• inherited inhibited heme biosynthesis

• Destroys RBCs

• Red teeth and urine

• madness

IMP biosynthesis

1. ribose-5-p bi-phosphorylated → PRPP limiting substance

2. Ammonia replaces biphosphate (committed step)

3. glycine added to ammonia group

4. fromyltetrahydrofolate donates formyl to N-terminal

5. Inner carbonyl group is converted to amidine

6. cyclization to imidazole ring

7. carboxylation of imidazole

8. carboxylate is displaced by amino group

9. fumarate leaves

10. formyl group added to amino group

11. dehydrated and cyclized

Azaserine

• antibiotic

• analog og glutamine

• inhibits purine synthesis by blocking aminotransferases