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1. BIOCHEMISTRY OF PORPHYRINS
DAVID MANYIEL AGOK (DMLT@RHSI)

2. LEARNING OBJECTIVES
1. Introduction
2. Structure
3. How porphyrin is made
4. Haem
5. Porphyrin Function

3. Introduction
Acyclic compounds.
Each porphyrin molecule is made up of 4 pyrrole rings.
The rings are linked by methylene (=HC-) bridge.
Commonly found in Heme and Chlorophyl molecules.
Structure
Porphyrins have complex cyclic structure.
Structurally, porphyrin consists of four pyrrole rings linked to each other by
methylene linkage (-CH=).
Pyrrole is a five-membered closed structures containing one nitrogen and four
carbon atoms.

4. How Porphyrin is Made
A porphyrin is a large ring molecule consisting of a pyrroles, which are smaller rings
made from 4 carbons and 1 nitrogen.

5. Haem
Porphyrin molecule.
It has a tetrapyrrole ring.
4 pyrrole rings are inter-connected by methylene bridges.
The ring also contains; Vinyl groups(-CH=CH₂), Methyl group(-CH₃), Propionyl
groups(-CH₂-CH₂-COOH)
An iron atom is kept in the centre of the porphyrin ring by interaction with the
four nitrogen atoms.
Sites of Heme biosynthesis are Erythroid cells and liver.
It gives red colour to the blood.

6. Steps of Heme Synthesis
Step 1: Formation of δ-amino Levulinic acid (ALA):
= Glycine + Succinyl-coA  δ-amino Levulinic acid + CO₂ + CoenzymeA
Step 2: Formation of Porphyrinogen:
= 2(δ-amino Levulinic acid)  Porphobilinogen + H₂O
Step 3: Formation or Uroporphyrinogen:
= 4(Porphobilinogen)  Uroporphyrinogen-III
Step 4: Formation of Heme:
= Uroporphyrinogen-III Protoporphyrin-IX + 6 Carbondioxide
= Protoporphyrin-IX + Fe⁺³  HEME

7. Porphyrin Function
The porphyrin ring in haem molecule serves as an important function.
The nitrogen molecule at the centre of the ring holds an iron molecule.
The porphyrin structure holding iron molecule gives blood its red colour.