Thursday, August 12, 2010


                Proteins are aminoacid polymers. In addition to the protein part most of the proteins contains some non-protein component. Such proteins are known as ' conjugated proteins". The protein part is known as "apoprotein". The non-protein component is known as "prosthetic group". If the prosthetic group is a metal atom then the conjugated protein is known as " metalloprotein".
                Metalloproteins are classified on the basis of their function as folloes:
  • Respiratory proteins
  • Electron transport proteins
  • Metal storage proteins
  • Catalytic proteins
                      These are metalloproteins which are involved in gas transport. Example : Hemoglobin, Myoglobin, Hemerythrin and Hemocyanin. Both hemoglobin and myoglobin are heme (prosthetic group) proteins containing Fe2+ . In higher animals hemoglobin transports oxygen from lungs to tissues. Myoglobin stores the oxygen in the tissues. Hemerythrin and hemocyanin are the oxygen carrying proteins of lower animals. Hemerythrin is a nonheme iron containing protein. Hemocyanin is a nonheme copper containing protein.

                       These are metalloproteins which are involved  in electron transport. They are the components of electron transport chain (ETC). Example: Cytochromes, iron sulphur protein and blue copper protein. Cytochromes (a, b, c) are the iron containing heheproteins that act as electron carrier in all aerobic forms of life. Iron sulphur proteins (Rubredoxin, ferridoxin) are nonheme proteins involved in electron transfer. Blue copper proteins (stellocyanin, plastocyanin, azurin) are nonheme copper containing proteins involved in electron transfer.

                        These are metalloproteins which are used to store the surplus metal in nontoxic form. Example: Ferritin, Transferrin (iron storage protein) Ceruloplasmin (copper storage protein).

                          Enzymes are otherwise known as catalytic proteins. Many enzymes contain metal ions as their structural component. Example: Cytochrome oxidase (iron and copper), Super oxide dismutase (copper and zinc), Nitrogenase (iron and molybdenum). These enzyme are bimetalcomplexes.

Excess and defiency of trace metals

  1. Copper deficiency results in loss of weight and death.
  2. Severe deficiency of copper causes demineralization of bones.
  3. Copper deficiency produces anemia. This cannot be treated by administration of iron.
  4. Copper deficiency results in hypopigmentation of skin.
  5. Copper deficiency produces Menke's disease or Kinky or Steel hair syndrome. Its symptoms are anemia and depigmentation of hair.
  6. The formation of elastin and collagen are impaired in copper deficiency.
  7. Copper deficiency results in the myocardial fibrosis.
  8. Wilson's disease is associated with low levels of copper and ceruloplasmin in the blood and increased copper deposition in kidney, liver, brain, and comea.
  9. Abnormal levels of serum copper leads to irritation of the gastrointestinal tract.
  1. Zinc deficiency results in dwarfism.
  2. There is loss of taste.
  3. Zinc deficiency causes poor growth and loss of appetite.
  4. Zinc deficiency produces dermatitis (lesions in the skin ).
  5. Zinc deficiency leads to the formation of immature gonads (sex glands).
  6. Deficiency of zinc obstracts the storage and secretion of insulin and causes diabetes mellitus.
  7. Zinc deficiency is associated with myocardial infarction and cirrhosis of liver.
  8. Zinc toxicity is associated with nausea (vomitting), gastric ulcer, anemia and excessive salivation.
  1. Iron deficiency leads to anemia. In such conditions the hemoglobin content of blood becomes 5-9g / 100ml of blood.(normal level of hemoglobin is 15 %).
  2. Iron deficiency leads to giddiness.
  3. In severe cases there may be oedema of the ankles.
  4. Iron deficiency leads to loss of appetite and retarted growth.
  5. iron toxicity leads to excessive deposition of iron in ferritin and hemosiderin (iron storage proteins). This disorder is known as hemosiderosis. This is common in patients receiving repeated blood transfusions.
  6. Iron toxicity produces another disorder known as hemochromatosis. Accumulation of iron in liver, pancreas and skin produces cirrhosis (liver disorder), bronze diabetes and bronze-state pigmentation respectively. 
  1. Manganese deficiency leads to retarded growth and bone deformities.
  2. Severe manganese deficiency leads to sterility.
  3. Its deficiency leads to accumulation of fat in liver.
  4. Deficiency of manganese results in the abnormal functioning of central nervous system.
  5. Manganese deficiency causes increased activity of serum alkaline phosphatase.
  6. Reduced activity of pancreas is associated with manganese deficiency. So insulin production is reduced.
  7. Manganese deficiency in plants affects photosynthesis.
  8. Manganese toxicity produces symptoms similar to Parkinson's disease.
  1. Deficiency of molybdenum results in lowered growth and increased mortality rate.
  2. Its deficiency affects nitrogen fixation in plants.
  3. Its deficiency affects plant growth.
  4. Toxicity of molybdenum is known as molybdenosis. The symptoms are diarrhoea, anemia and impairment in growth.
  5. Toxicity of molybdenum produces copper deficiency.
  1. Cobalt deficiency causes anorexia (loss of desire to eat).
  2. Its deficiency produces fatty liver (liver disorder).
  3. Cobalt deficiency results in macrocytic anemia (anemia due to large size of red blood cells)
  4. Cobalt deficiency produces hemosiderosis of spleen.
  5. Cobalt toxicity causes polycythemia (increased number of red blood cells).