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Dehydroalanine

Names
IUPAC name 2-Aminoprop-2-enoic acid
Identifiers
CAS Number	1948-56-7 Y
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:17123 Y
ChemSpider	110510 Y
DrugBank	DB02688 Y
KEGG	C02218 Y
PubChem CID	123991
InChI InChI=1S/C3H5NO2/c1-2(4)3(5)6/h1,4H2,(H,5,6) Y Key: UQBOJOOOTLPNST-UHFFFAOYSA-N Y InChI=1/C3H5NO2/c1-2(4)3(5)6/h1,4H2,(H,5,6) Key: UQBOJOOOTLPNST-UHFFFAOYAW
SMILES C=C(C(=O)O)N O=C(O)C(=C)N
Properties
Chemical formula	C3H5NO2
Molar mass	87.08 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Dehydroalanine (Cα,β-didehydroalanine, α,β-di-dehydroalanine, 2-aminoacrylate, or 2,3-didehydroalanine) is a dehydroamino acid. It exists both in its free form, produced by some pyridoxal 5'-phosphate-dependent α,β-eliminases^[1], and as a residue found in peptides of microbial origin. It is unusual in having an unsaturated backbone.^[2]

Structure and reactivity

As a primary enamine, dehydroalanine is unstable with respect to tautomerization. It therefore does not exist in large amounts or as a stable pure substance. However, N-acylated derivatives, such as peptides and related compounds, are stable.

Despite its name, dehydroalanine is not derived biochemically from alanine. Instead, it arises via a post translational modification of serine or cysteine. These amino acids, as residues in peptide chains, undergo enzyme-mediated loss of water and hydrogen sulfide, respectively.

Most amino acid residues are unreactive toward nucleophiles, but those containing dehydroalanine or some other dehydroamino acids are exceptions. These are electrophilic due to the α,β-unsaturated carbonyl,^[2] and can, for example, alkylate other amino acids. This activity has made DHA useful synthetically to prepare lanthionine.

Occurrence

The dehydroalanine residue was first detected in nisin, a cyclic peptide with antimicrobial activity.^[2] Dehydroalanine is also present in some lantibiotics and microcystins.

DHA can be formed from cysteine or serine by simple base catalysis without the need for an enzyme, which can happen during cooking and alkaline food preparation processes. It can then alkylate other amino acid residues, such as lysine, forming lysinoalanine cross-links and racemization of the original alanine. The resulting proteins are have lower nutritional quality for some species but higher nutritional quality for others. Some lysinoalanines may also cause kidney enlargement in rats.^[3]

Many dehydroalanine-containing peptides are toxic.^{[citation needed]}

A dehydroalanine residue was long thought to be an important electrophilic catalytic residue in histidine ammonia-lyase and phenylalanine ammonia-lyase enzymes, but the active residue was later found instead to be a different unsaturated alanine derivative—3,5-dihydro-5-methyldiene-4H-imidazol-4-one—that is even more electrophilic.^[4][5]

References