Flashcards in Selenium Deck (19)
Selenomethionine (supplements, plants)
Carbon bonding. Already replaced sulfur.
Selenium within the structure or Se dependent proteins.
Fish (if low Mercury)
>80% selenoamino acids (selenomethionine > selenocysteine)
50-90% selenate & selenite
Vitamins A, C, and E.
Reduced glutathione in intestinal lumen.
Heavy metals, especially Mercury.
Phytic acid (via chelation and precipitation).
Forms in the liver from organic and inorganic forms of selenium.
Antioxidant and transporter.
Contains most of the body's selenium 50-80% plasma
3 hour half life
Protects against lipid radicals (peroxide & hydrogen-peroxide)
Spares vitamin E
Assess Se status
Transports 10-30% of Se in plasma
Where is selenium stored?
Dietary selenocysteine cannot be used by the body.
Organic. "21st" AA. Needed for Se-dependent proteins. Has its own tRNA.
Catabolized into (inorganic) selenide.
Either methylated to be excreted via urine. Or converted back to selenocysteine (endogenous).
Enters AA pool. Used for protein synthesis.
Catabolized to make selenocysteine.
Best absorbed form of all selenoproteins.
Selenoamino acid are transported across basolateral membrane via AA transporters.
No one knows how inorganic selenium is transported.
When selenium binds to mercury, it prevents mercury from being absorbed.
Mercury can replace selenium which means selenoproteins cannot develop. Mercury poisoning.
Go directly to selenium pool and readily available.
Not incorporated into AA.
Pills, animal feed, cabbage, beets, yeast.
Either selenocysteine or an inorganic selenium is optimal.
Inorganic is directly available for use.
Selenomethionine is stored in tissues and not readily used.
4. Endogenous Selenocysteine.
5. Selenium dependent proteins produced.
Reduces glutathione using niacin
Helps reduce vitamin C and recycle it.
Iodothyronine 5' deiodinases
Helps remove iodine
Activates thyroid hormone to prevent goiter