Editing Amino acid (section)

==Synthesis==
{{Main|Amino acid synthesis}}

===Chemical synthesis===
The commercial production of amino acids usually relies on mutant bacteria that overproduce individual amino acids using glucose as a carbon source. Some amino acids are produced by enzymatic conversions of synthetic intermediates. [[2-Aminothiazoline-4-carboxylic acid]] is an intermediate in one industrial synthesis of [[cysteine|<small>L</small>-cysteine]] for example. [[Aspartic acid]] is produced by the addition of ammonia to [[fumarate]] using a lyase.<ref name=Ullmann>{{Ullmann | vauthors = Drauz K, Grayson I, Kleemann A, Krimmer HP, Leuchtenberger W, Weckbecker C |year=2007| doi=10.1002/14356007.a02_057.pub2|title=Amino Acids}}</ref>

===Biosynthesis===
In plants, nitrogen is first assimilated into organic compounds in the form of [[glutamate]], formed from alpha-ketoglutarate and ammonia in the mitochondrion. For other amino acids, plants use [[transaminase]]s to move the amino group from glutamate to another alpha-keto acid. For example, aspartate aminotransferase converts glutamate and oxaloacetate to alpha-ketoglutarate and aspartate.<ref>{{Cite book | vauthors = Jones RC, Buchanan BB, Gruissem W | title = Biochemistry & molecular biology of plants | publisher = American Society of Plant Physiologists | location = Rockville, Md | year = 2000 | pages = [https://archive.org/details/biochemistrymole00buch/page/371 371–372] | isbn = 978-0-943088-39-6 | url = https://archive.org/details/biochemistrymole00buch/page/371 }}</ref> Other organisms use transaminases for amino acid synthesis, too.

Nonstandard amino acids are usually formed through modifications to standard amino acids. For example, [[homocysteine]] is formed through the [[transsulfuration pathway]] or by the demethylation of methionine via the intermediate metabolite [[S-adenosylmethionine|''S''-adenosylmethionine]],<ref name="Brosnan">{{cite journal | vauthors = Brosnan JT, Brosnan ME | title = The sulfur-containing amino acids: an overview | journal = The Journal of Nutrition | volume = 136 | issue = 6 Suppl | pages = 1636S–1640S | date = June 2006 | pmid = 16702333 | doi = 10.1093/jn/136.6.1636S | doi-access = free }}</ref> while [[hydroxyproline]] is made by a [[post translational modification]] of [[proline]].<ref>{{cite book | vauthors = Kivirikko KI, Pihlajaniemi T | chapter = Collagen Hydroxylases and the Protein Disulfide Isomerase Subunit of Prolyl 4-Hydroxylases | title = Advances in Enzymology and Related Areas of Molecular Biology | volume = 72 | pages = 325–398 | year = 1998 | pmid = 9559057 | doi = 10.1002/9780470123188.ch9 | isbn = 9780470123188 | series = Advances in Enzymology – and Related Areas of Molecular Biology }}</ref>

[[Microorganism]]s and plants synthesize many uncommon amino acids. For example, some microbes make [[2-aminoisobutyric acid]] and [[lanthionine]], which is a sulfide-bridged derivative of alanine. Both of these amino acids are found in peptidic [[lantibiotics]] such as [[alamethicin]].<ref>{{cite journal | vauthors = Whitmore L, Wallace BA | title = Analysis of peptaibol sequence composition: implications for in vivo synthesis and channel formation | journal = European Biophysics Journal | volume = 33 | issue = 3 | pages = 233–237 | date = May 2004 | pmid = 14534753 | doi = 10.1007/s00249-003-0348-1 | s2cid = 24638475 }}</ref> However, in plants, [[1-aminocyclopropane-1-carboxylic acid]] is a small disubstituted cyclic amino acid that is an intermediate in the production of the plant hormone [[ethylene#Ethylene as a plant hormone|ethylene]].<ref>{{cite journal | vauthors = Alexander L, Grierson D | title = Ethylene biosynthesis and action in tomato: a model for climacteric fruit ripening | journal = Journal of Experimental Botany | volume = 53 | issue = 377 | pages = 2039–2055 | date = October 2002 | pmid = 12324528 | doi = 10.1093/jxb/erf072 | doi-access = free }}</ref>

===Primordial synthesis===
The formation of amino acids and peptides is assumed to have preceded and perhaps induced the [[abiogenesis|emergence of life on earth]]. Amino acids can form from simple precursors under various conditions.<ref name="10.1016/j.gsf.2017.07.007"/> Surface-based chemical metabolism of amino acids and very small compounds may have led to the build-up of amino acids, coenzymes and phosphate-based small carbon molecules.<ref>{{cite journal | vauthors = Danchin A | title = From chemical metabolism to life: the origin of the genetic coding process | journal = Beilstein Journal of Organic Chemistry | volume = 13 | issue = 1 | pages = 1119–1135 | date = 12 June 2017 | pmid = 28684991 | pmc = 5480338 | doi = 10.3762/bjoc.13.111 }}</ref>{{additional citation needed|date=September 2022}} Amino acids and similar building blocks could have been elaborated into proto-[[peptide]]s, with peptides being considered key players in the origin of life.<ref name="10.1021/acs.chemrev.9b00664">{{cite journal | vauthors = Frenkel-Pinter M, Samanta M, Ashkenasy G, Leman LJ | title = Prebiotic Peptides: Molecular Hubs in the Origin of Life | journal = Chemical Reviews | volume = 120 | issue = 11 | pages = 4707–4765 | date = June 2020 | pmid = 32101414 | doi = 10.1021/acs.chemrev.9b00664 | s2cid = 211536416 | bibcode = 2020ChRv..120.4707F }}</ref>

[[File:Strecker amino acid synthesis scheme.svg|class=skin-invert-image|thumb|upright=1.75 |right|The Strecker amino acid synthesis|alt=For the steps in the reaction, see the text.]]
In the famous [[Urey-Miller experiment]], the passage of an electric arc through a mixture of methane, hydrogen, and ammonia produces a large number of amino acids. Since then, scientists have discovered a range of ways and components by which the potentially prebiotic formation and chemical evolution of peptides may have occurred, such as condensing agents, the design of self-replicating peptides and a number of non-enzymatic mechanisms by which amino acids could have emerged and elaborated into peptides.<ref name="10.1021/acs.chemrev.9b00664"/> Several hypotheses invoke the [[Strecker synthesis]] whereby hydrogen cyanide, simple aldehydes, ammonia, and water produce amino acids.<ref name="10.1016/j.gsf.2017.07.007">{{cite journal |doi=10.1016/j.gsf.2017.07.007|title=Origins of building blocks of life: A review |year=2018 | vauthors = Kitadai N, Maruyama S |journal=Geoscience Frontiers |volume=9 |issue=4 |pages=1117–1153 |bibcode=2018GeoFr...9.1117K |s2cid=102659869 |doi-access=free }}</ref>

According to a review, amino acids, and even peptides, "turn up fairly regularly in the [[primordial soup|various experimental broths]] that have been allowed to be cooked from simple chemicals. This is because [[nucleotide]]s are far more difficult to synthesize chemically than amino acids." For a chronological order, it suggests that there must have been a 'protein world' or at least a 'polypeptide world', possibly later followed by the '[[RNA world]]' and the '[[DNA world]]'.<ref>{{cite journal | vauthors = Milner-White EJ | title = Protein three-dimensional structures at the origin of life | journal = Interface Focus | volume = 9 | issue = 6 | pages = 20190057 | date = December 2019 | pmid = 31641431 | pmc = 6802138 | doi = 10.1098/rsfs.2019.0057 }}</ref> [[Codon]]–amino acids mappings may be the [[biology|biological]] information system at the primordial origin of life on Earth.<ref>{{cite journal | vauthors = Chatterjee S, Yadav S | title = The Coevolution of Biomolecules and Prebiotic Information Systems in the Origin of Life: A Visualization Model for Assembling the First Gene | journal = Life | volume = 12 | issue = 6 | pages = 834 | date = June 2022 | pmid = 35743865 | pmc = 9225589 | doi = 10.3390/life12060834 | doi-access = free | bibcode = 2022Life...12..834C }}</ref> While amino acids and consequently simple peptides must have formed under different experimentally probed geochemical scenarios, the transition from an abiotic world to the first life forms is to a large extent still unresolved.<ref>{{cite journal | vauthors = Kirschning A | title = The coenzyme/protein pair and the molecular evolution of life | journal = Natural Product Reports | volume = 38 | issue = 5 | pages = 993–1010 | date = May 2021 | pmid = 33206101 | doi = 10.1039/D0NP00037J | s2cid = 227037164 | doi-access = free }}</ref>