Zn,Cu lecture(7) by Prof.Dr.Moaed Al-Gazally
Zinc"Zn": Zinc is found in biological systems only in the +2 valence state, so that biological oxidation-reduction function is not possible with Zn. The metabolic function of Zn are based on its 1. Presence as integral component of many metalo enzyme is the most important include, carbonic anhydrase, alkaline phosphatase, DNA &RNA polymerases, thymidine kinase Carboxy peptidase & alcohol dehydrogenase. The Zn atom are an integral, firmly bonds and are often involved in the active site they also contribute the confirmation and structural stability of many metalo enzymes. 2. Zn plays major role in protein synthesis & has an important function in gene expression. 3. Zn has been shown to be an important element in wound healing by affecting the biosynthesis &integrity of connective tissue. Metabolism: 1.4-2.3 g present in 70 kg adult. Prostate, liver , semen , kidney , bone &muscles are rich in Zn. The Zn contain of erythrocyte is about 10 times that if plasma best of their rich content of carbonic anhydrase &other Zinc containing enzymes. A proximal 20-30 % of ingested dieter Zn absorbed. The absorption process is active, energy dependent & mediated by specific transport (binding) ligand. High-protein foods such as meat, fish & diary products are good sources if available Zn- Diet rich in proteins stimulate Zn absorption, whereas diet low in proteins has the apposite effect. The RDA for Zn is 15 mg/day for adult males. Zn is transported in plasma mostly by albumin 60-70 % & by macro globulin 30-40 % & small amount with transferrin & amino acids. Clinical significant ? In mild Zn def, oligospormia , wt. loss & hyper amnonemia ? In moderate Zn def, growth retardation in children and adolescents, hypogonadism in males, mild dermatitis, poor appetite and delayed wound healing. ? In severe cases of Zn def, r dermatitis, wt loss, diarrhea, neuropsy chatric disorder recurrent infection & ultimality death if not treated. Besides nutritional factors many diseases & medial treatment may produce conditional Zn def.for eg: In hepatic cirrhosis, GIT disorders & in patients. Other causes of Zn def.(Iatrogenic) include administration of anabolic (steroids) & chelating drugs (pancillamine) In patient-receiving long-term-treatment with synthetic oral diets& total parental alimentation fluid are often trace element def.(Zn & others) Pregnant women are at higher risk of acquired Zn deficiency because of the high uptake of Zn by the fetus. Zn def. is also often associated with sickle cell anemia. ??????? Copper Is an essential trace element. It is required in the diet because it is the metal cofactor for a variety of enzymes. Copper accepts and donates electrons and is involved in reactions involving dismutation, hydroxylation, and oxygenation. However, excess copper can cause problems because it can oxidize proteins and lipids, bind to nucleic acids, and enhance the production of free radicals. It is thus important to have mechanisms that will maintain the amount of copper in the body within normal limits. The body of the normal adult contains about 100 mg of copper, located mostly in bone, liver, kidney, and muscle. The daily intake of copper is about 2–4 mg, with about 50% being absorbed in the stomach and upper small intestine and the remainder excreted in the feces. Copper is carried to the liver bound to albumin, taken up by liver cells, and part of it is excreted in the bile. Copper also leaves the liver attached ceruloplasmin, which is synthesized in that organ. Some Important Enzymes That Contain Copper. ................
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