Mineral metabolism (iodine & zinc) -Biochemistry


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metabolism of iodine and zinc (biochemistry)

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Mineral metabolism (iodine & zinc) -Biochemistry

  2. 2. INTRODUCTION What is minerals metabolism? Chemical processes undergo by minerals that occur within a living organism in order to maintain life IODINE Sources: Sea water, fish, cereals, vegetables and iodize salt ZINC Sources: legumes, potato, cabbage
  3. 3. IODINE  Biochemical function:  Formation of thyroid hormones  Thyroxine (T4)  Tri-iodothyronine (T3)  Total body contains: 25-30 mg of iodine  Normal level in blood: 5-10 mg/dL  80 % stored in the thyroid gland  Daily requirement: 150-200 µg/day
  4. 4. IODINE METABOLISM GOITROGENS - Ingredients in foodstuffs, which prevent utilization of iodine - Cassava, maize, millet, bamboo shoots, sweet potatoes and beans THIOCYANATE - Inhibits iodine uptake by thyroid - Cabbage and tapioca
  5. 5. THIOUREA - Inhibits iodination of thyroglobulin
  6. 6. Step 1: Uptake of Iodine Step 2: Oxidation of Iodine Step 3: Iodination Step 4: Coupling Step 5: Storage Step 6: Utilization Step 7: Hydrolysis Step 8: Release Step 9: Salvaging of iodine Step 10:Transport of thyroid hormones Step 11:Catabolism of thyroid hormones
  7. 7. Step 1: Uptake of iodine -thyroid gland takes up and concentrates iodine Inhibition: thiocyanate & perchlorate Stimulate:TSH Congenital defectiodine trapping,maybe treated by large doses of iodine
  8. 8. Step 2: Oxidation of iodine -oxidized to active form (I-  I+) *can only be performed in a thyroid -catalyzed by thyroperoxidase -NADPH-dependent reaction Inhibition: Antithyroid drugs; thiourea, thiouracil and methimazole Stimulate:TSH Congenital defectiodide oxidation defect, treatment withT4 is administered
  9. 9. Step 3: Iodination -Thyroglobulin (Tgb) is iodinated -Tgb secreted by the thyroid follicular cells -So 3,5-di-iodotyrosin (DIT) and 3- monoiodotyrosine (MIT) are produced
  10. 10. Step 4: Coupling  Location: in the border of the follicular cells  Some of the tyrosine residues in the thyroglobulin are aligned opposite to each other and are coupled.  When two DIT molecules couple, one molecule of tetraiodothyronine (T4) is formed.  Tri-iodo-tyronine (T3) may be formed by de-ionization of outer ring ofT4 by 5’-deiodinase.  Under normal condition,99% is produced byT4.  Iodotyrosyl coupling defect will be treated by giving T4
  11. 11. DEFICIENCY of IODINE Children  Cretinism Adults  Goiter  Hypothyroidism
  12. 12.  Myxedema
  13. 13. ZINC  As a cofactor:-  Carboxypeptidase A  DNA polymerase & RNA polymerase  Superoxide dismutase  Carbonic anhydrase  Total zinc content of body: 2g (60% in skeletal muscle, 30 % in bones)  Daily intake for adults and children: 10 mg/day  Daily intake for lactation and pregnancy: 15-20 mg/day
  14. 14.  Highest concentration of zinc: hippocampus area of brain and prostatic secretion  Rich dietary sources: beans,nuts,cheese,meat and shellfish  Copper,calcium,cadmiun,iron and phytate will interfere with absorption of zinc.  Zinc can be used to reduce copper absorption inWilson’s disease
  15. 15.  In liver, zinc is stored in combination with a specific protein, metallothionein.  Zinc is excreted through pancreatic juice and to a lesser extent through sweat.  Zinc stabilize insulin molecules in pancreas  Zinc containing protein (Gusten) in saliva is for taste sensation
  16. 16.  Zinc dependent enzymes: carboxypeptidase, carbonic anhydrase, alkaline phosphatase, lactate dehydrogenase, ethanol dehydrogenase, glutamate dehydrogenase and superoxide dismutase.
  17. 17. Zinc toxicity  intake > 1000 mg/day  Inhalation of zinc oxide fumes  Rat poisons  Chronic toxicity can lead to gastric ulcer, pancreatitis, anemia, nausea, vomiting and pulmonary fibrosis.  Acute toxicity is manifested as fever, excessive salivation, headache and anemia
  18. 18. DEFICIENCY of ZINC  Poor growth  Hypogonadism  Impaired wound healing  Reduction in number ofT and B lymphocytes  Depression, dementia and other psychiatric disorders  Impotence in male
  19. 19. REFERENCES  Vasudevan, D., S, S., &Vaidyanathan, K. (2013).Textbook of biochemistry for medical students.New Delhi: Jaypee Brothers Medical Publishers (P) Ltd.
  20. 20. Thank you