Back حمض أميني ضروري Arabic Незаменныя амінакіслоты Byelorussian Незаменими аминокиселини Bulgarian Esencijalna aminokiselina BS Aminoàcid essencial Catalan Esenciální aminokyseliny Czech Essentiel aminosyre Danish Essentielle Aminosäure German Βασικό αμινοξύ Greek Enda aminoacido Esperanto
An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized from scratch by the organism fast enough to supply its demand, and must therefore come from the diet. Of the 21 amino acids common to all life forms, the nine amino acids humans cannot synthesize are valine, isoleucine, leucine, methionine, phenylalanine, tryptophan, threonine, histidine, and lysine.[1][2]
Six other amino acids are considered conditionally essential in the human diet, meaning their synthesis can be limited under special pathophysiological conditions, such as prematurity in the infant or individuals in severe catabolic distress.[2] These six are arginine, cysteine, glycine, glutamine, proline, and tyrosine. Six amino acids are non-essential (dispensable) in humans, meaning they can be synthesized in sufficient quantities in the body. These six are alanine, aspartic acid, asparagine, glutamic acid, serine,[2] and selenocysteine (considered the 21st amino acid). Pyrrolysine (considered the 22nd amino acid),[3] which is proteinogenic only in certain microorganisms, is not used by and therefore non-essential for most organisms, including humans.
The limiting amino acid is the essential amino acid which is furthest from meeting nutritional requirements.[4] This concept is important when determining the selection, number, and amount of foods to consume because even when total protein and all other essential amino acids are satisfied if the limiting amino acid is not satisfied then the meal is considered to be nutritionally limited by that amino acid.[3]
- ^ Young VR (1994). "Adult amino acid requirements: the case for a major revision in current recommendations". J. Nutr. 124 (8 Suppl): 1517S–1523S. doi:10.1093/jn/124.suppl_8.1517S. PMID 8064412.
- ^ a b c Otten, Jennifer J.; Hellwig, Jennifer Pitzi; Meyers, Linda D., eds. (2006) [1943]. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements (Technical report). doi:10.17226/11537. ISBN 978-0-309-15742-1.
- ^ a b Lopez, Michael J.; Mohluddin, Shamim S. (18 March 2022). Biochemistry, Essential Amino Acids (Technical report).
- ^ "Limiting Amino Acids". National Agricultural Library. 30 November 2012. Retrieved 19 September 2022.