is the analog of cysteine having the same structure as that of cysteine. But here sulphur atom is replaced by selenium. The Health Store Selenocysteine is the 21st found in the ribosome mediated . It is present in several enzymes (for example , tetraiodothyronine 5′ , thioredoxin reductases, formate dehydrogenases, glycine reductases, and some hydrogenases). Selenocysteine has a structure similar to that of cysteine, but with an atom of taking the place of the usual sulfur, forming a group which is deprotonated at . Proteins that contain one or more selenocysteine residues are called . There is no single free pool of selenocysteine amino acid that exists within cells to be used
Selenocysteine is the protein, or food form, of the antioxidant selenium, and it is used in almost every cell process in the body. It is one of the only amino acids that is not directly coded into the genetic code, and no free pool of selenocysteine exists within cells to be used. This means that it is an essential amino acid and must be absorbed by cells and obtained through foods to maintain proper levels in the body. The body uses the selenocysteine amino acid to produce selenium. It is believed that this may protect against mercury toxicity, and people with low levels of selenium in their body may be more prone to poor liver function, low muscle mass, premature aging, and even heart disease.
Selenocysteine is created after the digestive system breaks proteins from the diet into its individual amino acids. Selenocysteine is a genetically coded amino acid, serving as a stop codon. Stop codons signal amino-acid chains, which will become proteins, to stop growing, releasing the protein to perform its intended function in the body. Selenoproteins are formed when the amino acid selenocysteine — often called the 21st amino acid — combines with selenium from the diet in a very specific spot in the amino-acid chain.
Functions and benefits Selenocysteine
- The important functions of selenocysteine in proteins are its anti –oxidant activity. This is due to its lower pKa and higher reduction potential.
- It is also used in the preparation of variety of vitamins and lots of other supplements.
- It is also fortified with livestock feeds.
- Our body utilizes selenocysteine to form selenium, which is believe to play important role in preventing mercury toxicity as well as enhance liver functions.
- Selenocysteine is not directly incorporated into other proteins. It provides its function on its own. For this reason it is highly reactive and not used in the same way as the body uses other amino acids.
- In some cases a marked decrease in catalytic activity of an enzyme is observed when a selenocysteine residue is replaced with cysteine. This substitution caused complete loss of glycine reductase selenoprotein A activity.
- Selenocysteine is the 21st naturally occuring amino acid, and is coded for by the RNA codon UGA, which is normally a “stop” signal, but is modified in some organisms to create selenocysteine by a subsequent RNA loop, which is interpreted by a group of genes called the sel group, which are activated by the loop in the mRNA and produce molecule of tRNA for selenocysteine.
- People deficient with selenium have lean body mass, prone to premature aging.
- Weaken the immune system, making the body more susceptible to illness, as well as lead to heart disease or hypothyroidism.
Rich food sources of Selenocysteine
- Animal origin: Selenocysteine animal sources are meat, poultry, chicken, egg, cheese fish, seafood and turkey.
- Plant origin: Selenocysteine of plant origin contains wheat, oats, corn, rice, nuts especially of Brazil nuts, soybeans.
- Selenocysteine is an organic selenium compound found naturally in some plants such as garlic, onions, broccoli and wild leeks grown in high selenium soil.
- Selenium: The trace element that act as an antioxidant in the body. (blissreturned.wordpress.com)
- Cysteine: The amino acid that helps to detoxify harmful toxins and protect the body from radiation damage. (blissreturned.wordpress.com)