Porphyrins

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Porphyrins

  1. 1. PORPHYRINS
  2. 2. Synthesis of porphyrins occurs in animals for haem production and in plants for chlorophyll production.
  3. 3. STRUCTURE  Porphyrins are cyclic tetrapyrroles in which the pyrrole rings, conventionally designated as A, B, C and D, are linked through their carbon atoms by methene (–CH=) bridges*.
  4. 4.  Porphyrins emit intense red fluorescence when exposed to light at around 400 nm. Thus, spectrofluorometric methods provide very sensitive detection and quantification of porphyrins  The porphyrin isomers differ in the arrangement of the side-chain substituents (e.g. acetyl and propionyl in uroporphyrins; methyl and propionyl in coproporphyrins) *.
  5. 5.  Porphyrins are differentiated by the kind and order of substitutes occupying the 8 peripheral position of pyrole rings of porphyrins .  Of many kinds of porphyrins found in nature, only uroporphyrin caproporphyrin and protoporphyrin have clinical significance. *
  6. 6. SYNTHESIS *
  7. 7.  In mammalian cells, haem synthesis occurs mostly in liver and erythropoietictissues (the erythropoietic cells (80%) and the liver parenchymal cells (20%))  The biosynthetic pathway starts in the mitochondrion and, after passing through three cytoplasmic stages, re-enters the mitochondrion for the final steps of haem formation.  Haemoproteins play very important roles in electron and oxygen transport, in the activation of oxygen or hydrogen peroxide and, finally, in hydrogen peroxide decomposition
  8. 8. **
  9. 9. REGULATION OF HAEM SYNTHESIS * Regulation of haem biosynthesis in the liver
  10. 10. Retroinhibition of hepatic ALAS1 activity via a negative feedback regulation mediated by the free intracellular haem pool.
  11. 11. BIBLIOGRAPHY * Puy, Hervé and Deybach, Jean-Charles. "Haem biosynthesis and excretion of porphyrins", [Documento en línea]. Gastrohep, online Resource for Gastroenterology, Hepatology and Endoscopy. Dirección URL: <http://www.gastrohep.com/ebooks/rodes/Rodes_2_3_10.pdf>. ** King, Michael W. Ph.D. Iron, Heme and Porphyrin Metabolism, [Documento en línea]. The Medical Biochemistry Page. Dirección URL: <http://themedicalbiochemistrypage.org/heme- porphyrin.html>.

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