MINERAL METABOLISM

IODINE & ZINC

MARYAM JAMILAH BINTI ABDUL HAMID082013100002

IMS BANGALORE

INTRODUCTIONWhat 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

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

IODINE METABOLISM

GOITROGENS- Ingredients in foodstuffs, which

preventutilization of iodine

- Cassava, maize, millet, bamboo shoots, sweet potatoes and beans

THIOCYANATE- Inhibits iodine uptake by thyroid- Cabbage and tapioca

THIOUREA- Inhibits iodination of

thyroglobulin

Step 1: Uptake of IodineStep 2: Oxidation of IodineStep 3: IodinationStep 4: CouplingStep 5: StorageStep 6: UtilizationStep 7: HydrolysisStep 8: ReleaseStep 9: Salvaging of iodineStep 10:Transport of thyroid hormonesStep 11:Catabolism of thyroid hormones

Step 1: Uptake of iodine

-thyroid gland takes up

and concentrates iodine

Inhibition:

thiocyanate & perchlorate

Stimulate: TSH

Congenital defectiodine

trapping,maybe treated

by large doses of iodine

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 defectiodide oxidation

defect, treatment with T4 is

administered

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

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 of T4 by 5’-deiodinase.

Under normal condition,99% is produced by T4.

Iodotyrosyl coupling defect will be treated by giving T4

DEFICIENCY of IODINE

Children

Cretinism

Adults

Goiter

Hypothyroidism

Myxedema

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

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 in Wilson’s disease

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

Zinc dependent enzymes:

carboxypeptidase, carbonic anhydrase,

alkaline phosphatase, lactate

dehydrogenase, ethanol dehydrogenase,

glutamate dehydrogenase and superoxide

dismutase.

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

DEFICIENCY of ZINC

Poor growth

Hypogonadism

Impaired wound healing

Reduction in number of T and B lymphocytes

Depression, dementia and other psychiatric

disorders

Impotence in male

REFERENCES

Vasudevan, D., S, S., & Vaidyanathan, K. (2013).Textbook of biochemistry for medical students.New Delhi: Jaypee Brothers Medical Publishers (P) Ltd.

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