Selenocysteine Synthesis/ Selenoproteins uses and Defiency Symptoms| Harper's Chapter 27| Lec 8/9

Описание: Selenocysteine, Selenoproteins & Deficiency Symptoms Explained
Description:
Selenocysteine, often called the 21st amino acid, is unique because it is directly incorporated into proteins during translation. Unlike standard amino acids, selenocysteine is synthesized on its specific tRNA and requires a special recoding of the UGA stop codon. This process depends on selenium, an essential trace element.
Synthesis of Selenocysteine:
Selenocysteine is synthesized on its tRNA^Sec.
Serine is first attached to tRNA^Sec.
The serine is then enzymatically converted to selenocysteine using selenophosphate as the selenium donor.
The UGA codon in mRNA is recoded to insert selenocysteine instead of signaling translation termination.
Uses of Selenoproteins:
Selenoproteins are crucial for various physiological processes:
Glutathione peroxidases (GPx): Protect cells from oxidative stress.
Thioredoxin reductases: Maintain redox balance and regulate cell signaling.
Iodothyronine deiodinases: Activate and deactivate thyroid hormones.
Other selenoproteins: Involved in reproduction, immune function, and muscle metabolism.
Deficiency Symptoms of Selenium/Selenoproteins:
Cardiomyopathy (Keshan disease)
Impaired thyroid hormone metabolism (hypothyroidism)
Increased oxidative stress and susceptibility to infections.

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