What are amino acids?

Amino acids are relatively simple molecules containing both amino (NH2) group and carboxyl (COOH) functional groups. They are ancient, from an evolutionarily viewpoint, and, alongside carbohydrates and fatty acids, basic nutrients. Twenty amino acids provide minimal requirements for growth, nitrogen equilibrium, maintenance of host defenses, neural (Fernstrom, 2000; Young et al., 1994) and muscular functions, as well as gene expression regulation (Fafournoux et al., 2000). The catabolism of amino acids contributes an energy source via intermediate products of glycolytic pathways and the citric acid cycle. The body is incapable of storing large amounts of amino acids and their homeostasis must be finely maintained by the integrated action of all the tissue and organs. For this reason, the dietary requirement for amino acids has important health consequences (Rose, 1957; Millward, 1994; Young, 1998; Young and Borongha, 2000). Nine amino acids are considered essential to diet, but demarcation between essentiality and non-essentiality is blurred by discoveries that have revealed effects of age (Baertl et al., 1974; Schober et al., 1989), nutritional status (Kurpad et al., 2003), and psycho-behavioral conditions, such as exposure to severe stress (Lacey and Wilmore, 1990; Obled et al., 2002). Indeed, the 2007 report of a joint WHO/FAO/UNU expert consultation on “Proteins and Amino Acids Requirements in Human Nutrition” led to a dramatic increase in the requirements for almost all essential amino acids, reflecting the recent shift towards to the quality of protein human dietary supply.

Amino acids are also the biochemical building blocks of proteins (large, naturally occurring polypeptides). The protein chains are made by linking the amino group of one amino acid with the carboxyl group of another. The amino acids absorbed into the body are utilized for the reconstitution of the body’s own proteins. It is therefore essential that the amino acids, as substrates of proteins, exist in sufficient quantity and a proper balance. The history of the discovery of amino acids began with the isolation of asparagine from an extract of asparagus shoot in 1806 and came to an end with the discovery of threonine in 1935. The beginning of the industrial production goes back to 1909 when glutamic acid was first obtained by extraction from wheat gluten hydrolysate to be used as a flavor enhancer. In the 1950s, a progress in the technology of purification and isolation enlarged the scope of applications for numerous amino acids, especially for those amino acids produced by fermentation. Presently, four methods of production are being used, extraction, fermentation, enzymatic method and chemical synthesis.

Since 1956, crystalline amino acids have been used in the medical and pharmaceutical fields as components of parenteral and later also enteral nutrition. For example, high quality amino acids have been employed for nutritional therapy in the treatment of patients with inflammatory bowel disease, Crohn’s disease or food allergies. Some amino acids are being utilized as ACE inhibitors, HIV protease inhibitors, anti-viral agents or anti-diabetic drugs.

In many developed countries, amino acids have been long utilized as dietary supplements or important constituents of cosmetics among the general healthy population in sport nutrition, cardiovascular health, hematopoietics and so on.

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