Editing Peptide bond (section)

==Synthesis==
[[File:Peptidformationball.svg|thumb|right|Peptide bond formation via [[dehydration reaction]]]]
When two amino acids form a ''[[dipeptide]]'' through a ''peptide bond'',<ref name=":0" /> it is a type of [[condensation reaction]].<ref>{{Cite journal |last=Muller |first=P. |date=1994-01-01 |title=Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994) |journal=Pure and Applied Chemistry |volume=66 |issue=5 |pages=1077–1184 |doi=10.1351/pac199466051077 |s2cid=195819485 |issn=1365-3075|url=https://archive-ouverte.unige.ch/unige:151920 |doi-access=free }}</ref> In this kind of condensation, two amino acids approach each other, with the non-[[side chain]] (C1) [[carboxylic acid]] [[Functional group|moiety]] of one coming near the non-side chain (N2) [[amino]] moiety of the other. One loses a [[hydrogen]] and oxygen from its carboxyl group (COOH) and the other loses a hydrogen from its amino group (NH<sub>2</sub>). This reaction produces a molecule of water (H<sub>2</sub>O) and two amino acids joined by a peptide bond (−CO−NH−). The two joined amino acids are called a dipeptide.

The amide bond is synthesized when the [[carboxyl group]] of one amino acid molecule reacts with the [[amino group]] of the other amino acid molecule, causing the release of a molecule of [[water]] (H<sub>2</sub>O), hence the process is a [[dehydration synthesis]] reaction.
[[File:AminoacidCondensation.svg|thumb|center|The dehydration condensation of two [[amino acid]]s to form a peptide bond (red) with expulsion of water (blue)|590x590px]]
The formation of the peptide bond consumes energy, which, in organisms, is derived from [[Adenosine triphosphate|ATP]].<ref>{{cite book |last1=Watson |first1=James |last2=Hopkins |first2=Nancy |last3=Roberts |first3=Jeffrey |last4=Agetsinger Steitz |first4=Joan |last5=Weiner |first5=Alan |year=1987 |orig-date=1965 |title=Molecualar Biology of the Gene |type=hardcover |edition=Fourth |location=Menlo Park, CA |publisher=The Benjamin/Cummings Publishing Company, Inc. |page=[https://archive.org/details/molecularbiology0004unse/page/168 168] |isbn=978-0-8053-9614-0 |url=https://archive.org/details/molecularbiology0004unse/page/168 }}</ref> Peptides and [[protein]]s are chains of [[amino acid]]s held together by peptide bonds (and sometimes by a few [[isopeptide bond]]s). Organisms use [[enzyme]]s to produce [[nonribosomal peptide]]s,<ref>{{cite book |author=Miller B. R. |author2=Gulick A. M. | title = Nonribosomal Peptide and Polyketide Biosynthesis | chapter = Structural Biology of Nonribosomal Peptide Synthetases | series = Methods in Molecular Biology | volume = 1401 | pages = 3–29 | date = 2016 | pmid = 26831698 | pmc = 4760355 | doi = 10.1007/978-1-4939-3375-4_1 | isbn = 978-1-4939-3373-0 }}</ref> and [[ribosome]]s to produce proteins via reactions that differ in details from dehydration synthesis.<ref>{{cite book |author=Griffiths A. J. |author2=Miller J. H. |author3=Suzuki D. T. |author4=Lewontin R. C. |author5=Gelbart W. M. |date=2000 |title=Protein synthesis |url=https://www.ncbi.nlm.nih.gov/books/NBK22022/ |journal=An Introduction to Genetic Analysis |edition=7th | location = New York | publisher =  W. H. Freeman |isbn=978-0-7167-3520-5 }}</ref>

Some peptides, like [[alpha-amanitin]], are called ribosomal peptides as they are made by ribosomes,<ref>{{cite journal |author=Walton J. D. |author2=Hallen-Adams H. E. |author3=Luo H. | title = Ribosomal biosynthesis of the cyclic peptide toxins of Amanita mushrooms | journal = Biopolymers | volume = 94 | issue = 5 | pages = 659–664 | date = 2010 | pmid = 20564017 | pmc = 4001729 | doi = 10.1002/bip.21416 }}</ref> but many are [[nonribosomal peptide]]s as they are synthesized by specialized enzymes rather than ribosomes. For example, the tripeptide [[glutathione]] is synthesized in two steps from free [[amino acid]]s, by two [[enzyme]]s: [[glutamate–cysteine ligase]] (forms an [[isopeptide bond]], which is not a peptide bond) and [[glutathione synthetase]] (forms a peptide bond).<ref>{{cite journal |author=Wu G. |author2=Fang Y. Z. |author3=Yang S. |author4=Lupton J. R. |author5=Turner N. D. | title = Glutathione metabolism and its implications for health | journal = The Journal of Nutrition | volume = 134 | issue = 3 | pages = 489–492 | date = March 2004 | pmid = 14988435 | doi = 10.1093/jn/134.3.489 | doi-access = free }}</ref><ref>{{cite journal |author=Meister A. | title = Glutathione metabolism and its selective modification | journal = The Journal of Biological Chemistry | volume = 263 | issue = 33 | pages = 17205–17208 | date = November 1988 | pmid = 3053703 | doi = 10.1016/S0021-9258(19)77815-6 | url = https://www.jbc.org/article/S0021-9258(19)77815-6/fulltext | doi-access = free }}</ref>