Heme metabolism Dr. Vijay Marakala, MBBS, MD.

Assistant professor BIOCHEMISTRY SIMS & RC

Heme synthesis Heme

degradation

•Heme Metabolism

•Heme synthesis

Hemoglobin Heme Pyrrole

Tetrapyrrole Porphyrinogen

Haemoglobin

Hemoglobin

Functions 1. Delivery of O2 from the lungs to the tissues2. Transport of CO2 from the tissues to the lungs.

Haem •Heme is a member of a family of compounds called porphyrins.•Many important proteins contain heme as a prosthetic group.

Porphyrins • Porphyrins are cyclic compounds composed of 4 pyrole rings held together by methenyl bridges.

Porphyrins • Porphyrins are substituted at positions 1-8

•Porphyrins

•Porphyrins

Site Reactions

Regulation

•Haem synthesis

•Heme synthesis - site

Tissues

• Liver • Bone marrow

Cell

• Mitochondria • Cytoplasm

•Reactions of Heme synthesisSTEPS ALA synthesis

Formation of PorphobillinogenFormation of HydroxymrthylbilaneFormation of UroporphyrinogenSynthesis of CoproporphyrinogenSynthesis of ProtoporphyrinogenGeneration of ProtoporphyrinGeneration of Heme

ALA SYNTHASE

STEP 1

PBG

δ ALA DEHYDRATASE

2 δALA STEP 2

4 PBGSTEP 3

STEP 4

STEP 5

3

4

5

STEP 6

STEP 8

STEP 7

Regulation of heme synthesis