Porphyrin Rings

1. Porphyrin Rings Produced mainly in: Liver Erythrocyte producing cells of bone marrow Not mature erythrocytes (lack of mitochondria) Initial step and last three steps are in the mitochondria Glycine and Succinyl CoA are precursors Hemin is feedback inhibitor of ?-aminolevulinic dehydrase (ALA) (?-delta) Lead is inhibitor of this pathway

2. Porphyrin Uses Cytochromes P450, b5, ETS Hemoglobin

3. Porphyrin Pathway Begins in Mitochondria Vitamin necessary in first enzyme reaction Pyridoxal Phosphate Porphobilinogen is first molecule in cytosol

4. Porphyrins Cont: Addition of ferrous iron in mitochondria ferrochelatase

5. Porphyrias Usually hereditary porphyrin production defects General Classification Erythropoietic (defect in RBCs) Hepatic (Defect in liver) Usually autosomal dominant Covered in genetics

6. Heme Degradation First product is biliverdin (open ring) Heme oxygenase Biliverdin plus CO yields bilirubin Biliverdin reductase NADP Bilirubin Gut (microbial enzymes act on bilirubin) Produce Urobilinogen Absorbed and carried to liver to produce Urobilin Yellow color Large intestine further microbial enzymes produce Stercobilin Characteristic brown color Liver Conjugation with 2 moles of glucuronic acid Glucuronyl bilirubin transferase Forms bilirubin diglucuronide (polar and soluble) detox

7. Porphyrin Ring Breakdown

8. Jaundice Hemolytic Response to sickle cell anemia Glycolytic enzyme deficiencies Erythroblastosis foetalis Obstructive Hepatic tumor Pale stools GI pain, nausea Hepatocellular Liver damage Cirrhosis, hepatitis Urine dark, stools pale (liver regurgitates conjugated bilirubin into blood and then into urine) Elevated AST (SGOT) and ALT (SGPT)

9. Hemoglobin Porphyrin ring Iron Oxygen Binding Two alpha chains and two beta chains ?1?2?1?2 Thalassemias

10. Genetics of Hemoglobin ?1?2 Chromosome 16 Diploid designation ?1?2/?1?2 Produced in utero ?1?2 Chromosome 11 Produced postpartum only Alpha-like chains (?) pre- & post-natal ? (zeta) Beta-like chains (?) Essentially post-natal ??? (sigma, epsilon, gamma)

11. Hemoglobin Oxygen Release High acidity causes hemoglobin to release oxygen Erythrocytes passing through tissue that are producing acids-lactic acid Handoff to myoglobin Called Bohr effect (Christian Bohr-Physiologist) Named after father of noted physicist Niels Bohr 2,3-bisphosphoglycerate promotes release of oxygen by hemoglobin

12. Representation of pH and Oxygen Binding

13. Cooperative Oxygen Binding Myoglobin-rectangular hyperbola Hemoglobin-sigmoidal Partial pressure Saturation

14. Structure of Hemoglobin

15. Carbon Dioxide & Hb Isohydric Transport of CO2 Gas exchange without pH change Carbonic anhydrase (Zn-containing)

16. Another Mechanism of CO2 Transport Direct reaction of carbon dioxide to produce carbaminohemoglobin

17. Genetics Overview ?-psi pseudo-genes Mutations (mutated) such that they do not produce a functional protein ?-zeta

18. Hemoglobinopathies Very common AR-Sickle Cell Anemia HbA vs HbS (?6 Glu?Val) Life long hemolytic anemia

19. Hemoglobinopathies-Cont: Thalassemias (thalassa-sea:many cases around Mediterranian Sea) ?+ ?0 (some production vs. none) ?+ ?0(some production vs. none) Alpha thalassemias affect fetal and postpartum hemoglobin Beta thalassemias affect only postpartum

20. Thalassemias-Cont: Alpha thalassemia usually more severe Thalassemia major Variety of deletions (usually) Beta thalassemia usually less severe Thalassemia minor Usually single nucleotide substitutions

21. Iron Association with copper Absorption from lumen in intestine Ceruloplasmin Cupric to cuprous, ferrous to ferric Vitamin C Wilson�s disease 1:100,000 Lack of copper transport proteins

22. Iron Contained in:Some Examples Hemoglobin, myoglobin NO binding, guanylate cyclase ETS hemes Cytochrome b5 in desaturation Iron-sulfur (Complex I, aconitase, xanthine oxidase, ferrochelatase (heme synth.) Phenylalaine hydroxylase, tyrosine hydroxylase, dioxygenases Etc.

23. Proteins and Iron Iron binding proteins Transferrin (Fe3+), Lactoferrin (Fe3+), Ferritin (Fe3+), Hemosiderin (Fe3+) Proteins that use iron as substrate Ferroxidase (Fe2+/Fe3+)-adrenals, Ferrochelatase (Fe2+)-porphyrins Protein that uses heme as substrate Heme oxygenase (biliverdin)

24. Transferrin Plasma protein Glycoprotein synthesized by liver Single polypeptide (~700 AA�s) High affinity for ferric iron No affinity for ferrous iron Serum levels about 30umol/L Serum has excess iron binding capacity

25. Transferrin Cont: Transferrin production increased during Iron deficiency Pregnancy (high estrogen levels) Women taking oral contraceptives Transferrin production decreased Excess iron Infection Inflammation Neoplasia Protein catabolic state Transferred to recipient cells by- Transferrin-binding Receptors

26. Ferritin Store iron in ferrous non-toxic state Relatively short term storage Handoff to/from transferrin Handoff to/from hemosiderin Mainly intracellular Not usually in the serum unless iron storage saturation

27. Other Transport Proteins Exist during high iron overload, ineffective erythropoiesis (hemes/hemoglobin in serum), hemolytic anemia, etc. Examples Haptoglobin Bind free (serum) oxyhemoglobin dimers Brought into hepatocytes by receptor mediated endocytosis Hemopexin and albumen bind free hemes Lactoferrin (neutrophils, secretory epithelial secretions (milk)

28. Hemosiderin Long term storage Handoff to/from ferritin Exist in times of iron overload Probably a form of iron-ferritin complexes in a type of micelle formation in tissues

29. Iron in Foods

30. Hypochromic Anemia Pale RBCs due to low levels of hemoglobin

31. Hemochromatosis Excess iron (free iron due to saturation of tranferrin) Arthritis, liver cancer, coronary occlusions Early diagnosis and treatment AR inheritance with gene on chromosome 6 Treatment Venesection (removal of blood) Removal of 500ml of blood over specified frequency and period of time to lower iron reserves High frequency is 500ml per week over 1-2 year period of time Chelation

32. Assessment of Iron Serum Ferritin Concentration Quantitative relationship to iron stores 20-200ng/mL Remember:ferritin is usually tissue bound Note: Some research has shown a relationship between excess iron, and heart disease and cancer Supplement only when deficient

33. Copper in Enzymes