Markedly, amino acids are organic compounds that contain amine and carboxyl functional groups, along with a side chain specific to each amino acid. Most importantly, the key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen, although other elements are found in the side chains of certain amino acids.
Further they include the 22 proteinogenic (“protein-building”) amino acids, which combine into peptide chains (“polypeptides”) to form the building-blocks of a vast array of proteins. Amongst these, twenty of the proteinogenic amino acids are encoded directly by triplet codons in the genetic code and are known as “standard” amino acids. However, the other two (“non-standard” or “non-canonical”) are selenocysteine and pyrrolysine. Many important proteinogenic and non-proteinogenic amino acids have biological functions. In conclusion, in aqueous solution amino acids exist in two forms, the molecular form and the zwitterion form in equilibrium with each other.
For example, in the human brain, glutamate and gamma-amino butyric acid are, respectively, the main excitatory and inhibitory neurotransmitters. Moreover, Hydroxyproline, a major component of the connective tissue collagen, is synthesized from proline. Glycine is a biosynthetic precursor to porphyrins used in red blood cells. Furthermore, Carnitine is used in lipid transport. Lastly, The first few amino acids were discovered in the early 19th century. In 1806, French chemists Louis-Nicolas Vauquelin and Pierre Jean Robiquet isolated a compound in asparagus that was subsequently named asparagine, the first amino acid to be discovered.
- Firstly, essential amino acids
- Secondly, nonessential amino acids
- Thirdly, conditional amino acids
Besides, Lysine is an amino acid (building block of protein). People use it to make medicine. As well, lysine is used for preventing and treating cold sores (caused by the virus called herpes simplex labialis). Additionally, it is taken by mouth or applied directly to the skin topically for this use. Topical lysine, sold under the brand name LYCIMOND in India, an ointment used for wound healing. Specifically used in cases of burns, surgical post-operative wounds, apthous ulcers, herpes wounds, decubitus ulcers and other non healing wounds or ulcers.
Additinally, the human body cannot synthesize lysine. It is essential in humans and must be obtained from the diet. Overall, lysine catabolism occurs through one of several pathways, the most common of which is the saccharopine pathway. Having said that, lysine plays several roles in humans, most importantly proteinogenesis. But also in the crosslinking of collagen polypeptides, uptake of essential mineral nutrients, and in the production of carnitine.
Due to its importance in several biological processes, a lack of lysine can lead to several disease states including defective connective tissues, impaired fatty acid metabolism, anaemia, and systemic protein-energy deficiency. In contrast, an overabundance of lysine, caused by ineffective catabolism, can cause severe neurological disorders.
Nevertheless, Lysine was first isolated by the German biological chemist Ferdinand Heinrich Edmund Drechsel in 1889 from the protein caesin in milk. Eventually, he named it “lysin“. In 1902, the German chemists Emil Fischer and Fritz Weigert determined lysine’s chemical structure by synthesizing it.
Chiely, good sources of lysine are high-protein foods such as eggs, meat (specifically red meat, lamb, pork, and poultry), soy, beans and peas, cheese (particularly Parmesan), and certain fish. Although, a food is considered to have sufficient lysine if it has at least 51 mg of lysine per gram of protein (so that the protein is 5.1% lysine).
Yet, there has been a long discussion that lysine, when administered intravenously or orally, can significantly increase the release of growth hormones. Because herpes simplex virus (HSV) proteins are richer in arginine and poorer in lysine than the cells they infect, lysine supplements have been tried as a treatment. Since the two amino acids are taken up in the intestine, reclaimed in the kidney, and moved into cells by the same amino acid transporters, an abundance of lysine would, in theory, limit the amount of arginine available for viral replication.
Overall, the role of lysine in collagen has been outlined above, however, a lack of lysine and hydroxylysine involved in the crosslinking of collagen peptides has been linked to a disease state of the connective tissue. Inspite, Lysine has also been shown to play a role in anaemia, as lysine is suspected to have an effect on the uptake of iron and, subsequently, the concentration of ferritin in blood plasma.
Therefore, Lysine production for animal feed is a major global industry, reaching in 2009 almost 700,000 tonnes for a market value of over €1.22 billion. As well, Lysine is an important additive to animal feed because it is a limiting amino acid when optimizing the growth of certain animals such as pigs and chickens for the production of meat.