Selenium Metabolism ( Rajeev Gandham )

Selenium

• Selenium was found to prevent liver cell necrosis & muscular dystrophy.

• Total body content of selenium around 10 mg and it is present mainly in liver.

• Sources:

• Richest sources are meat, sea foods, liver,
kidney and grains.

• RDA

• 50 to 200 μg/day.

Absorption and excretion

• Selenium is absorbed mainly from the duodenum.

• Selenium after absorption is transported bound to plasma proteins particularly β- lipoproteins in humans.

• Main route of excretion of selenium appears to be through urine.

Functions

• Selenium, as selenocysteine is an essential component of the enzyme glutathione peroxidase.

• Glutathione peroxidase functions as an antioxidant enzyme.

• It suppresses the oxidative stress by converting oxygen free radicals into less toxic forms or non-toxic forms.

• The presence of selenium in the diet reduces the requirement of vitamin E, since vitamin E also acts as an antioxidant.

• Selenium may exert anticancer effects because of its antioxidant role.

• Selenium containing enzyme 5’deiodinase converts thyroxine (T4) to triiodo-thyronine (T3) in thyroid gland.

• In selenium deficiency, conversion of T4 to T3 is
impaired resulting in hypothyroidism.

• Selenium binds with certain heavy metals & protects body from their toxic effects.

• Selenocysteine is considered as 21st standard amino acid since it is coded by UGA, which is a termination codon.

• Selenium is incorporated to proteins as selenocysteine during protein synthesis.

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