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11 Cards in this Set

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How is Se homeo maintained?
Via urinary excretion as trimethyl Se
Name some Se-dependent enzymes
Glutathione Peroxidases (3)
Iodothyronine deiodinase
Thioredoxin reductase
What are the Gluthathione peroxidases?

What role does Se play?
cGSH-Px - cellular (widespread)
eGSH-Px - extracellular (plasma & milk)
phGSH-Px - phospholipid hydroperoxide

**Se is at active site
What is their role?
ROOH + 2GSH --> GSSG + ROH + H20
Catalyzes hydroperoxide reaction.
What is special about ph-GSH-Px?
It can react w/FA hydroperoxides esterified onto phospholipids.
What is the role of Iodothyronine deiodinase?
Deiodinized T4-->T3
Circulating to active form.
What is the role of Thioredoxin reductace?
Catalyzes recution ofThioredoxin (NADH dependent)
Describe the synthesis of selenocysteine?
Selenocysteine the Se-containing AA in aminals.

tRNA is first charged with serine.: ser + tRNA --> ser-tRNA

Then, it reacts with Se (Selenophosphate actually) --> Sec-tRNA

Sec is encorporated into protens during translation.

Sec is
How is selenophosphate created?

What is the enzyme?
Selenine (O=Se-(OH)2) --> O=Se-OH-OPO3 via selenophosphate synthetase ( a Se containing protein!)
Descibe how sec gets incorporated.
mRNA codes for sec using stop codon "UGA". However, unique stem-loop struction on the mRNA causes UGA to be read as "include sec" and not "stop"
What is the deficiency of Se called?

What are the symptoms?
Keshan's disease

Coughing, difficulty breathing, vomiting. Swollen body, enlarged liver, lungs. Also: cardiomyopathy -very serious and often fatal.