biochemistry Biochemistry, or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology, a ...

, a dehydroamino acid or α,β-dehydroamino acid is an amino acids, usually with a C=C double bond in its side chain. Dehydroamino acids are not coded by DNA, but arise via

post-translational modification In molecular biology, post-translational modification (PTM) is the covalent process of changing proteins following protein biosynthesis. PTMs may involve enzymes or occur spontaneously. Proteins are created by ribosomes, which translation (biolog ...

Examples

A common dehydroamino acid is

dehydroalanine Dehydroalanine (Cα,β-didehydroalanine, α,β-di-dehydroalanine, 2-aminoacrylate, or 2,3-didehydroalanine) is a dehydroamino acid. It does not exist in its free form, but it occurs naturally as a residue found in peptides of microbial origin. As ...

, which otherwise exists only as a residue in proteins and peptides. The dehydroalanine residue is obtained dehydration of

serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − ...

-containing protein/peptide (alternatively, removal of H₂S from

cysteine Cysteine (; symbol Cys or C) is a semiessential proteinogenic amino acid with the chemical formula, formula . The thiol side chain in cysteine enables the formation of Disulfide, disulfide bonds, and often participates in enzymatic reactions as ...

). Another example is dehydrobutyrine, derived from dehydration of

threonine Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form when dissolved in water), a carboxyl group (which is in the deprotonated −COO− ...

. Generally, amino acid residues are unreactive toward nucleophiles, but the dehydroamino acids are exceptions to this pattern. For example, dehydroalanine adds cysteine and lysine to form covalent crosslinks. An unusual dehydroamino acid is

dehydroglycine Dehydroglycine is the organic compound with the formula . This rarely observed species is invoked as the product of oxidation (dehydrogenation) of glycine by glycine oxidase (ThiO), which is a step in the biosynthesis of thiamin. It is also inv ...

(DHG) because it does not contain a carbon-carbon double bond. Instead it is the

imino acid In organic chemistry, an imino acid is any molecule that contains both imine (>C=NH) and carboxyl (-C(=O)-OH) functional groups. Imino acids are structurally related to amino acids, which have amino group instead of imine—a difference of ...

glyoxalic acid Glyoxylic acid or oxoacetic acid is an organic compound. Together with acetic acid, glycolic acid, and oxalic acid, glyoxylic acid is one of the C2 carboxylic acids. It is a colourless solid that occurs naturally and is useful industrially. Str ...

. It arises by the radical-induced degradation of

tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a conditionally essential amino acid with a polar side group. The word "tyrosine" is ...

N-Acyl derivatives

Dehydroamino acids do not feature amino-alkene groups, but the corresponding N-acylated derivatives are known. These derivatives, also known as N-acylamino acrylates, are prochiral substrates for

asymmetric hydrogenation Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen to a target (substrate) molecule with three-dimensional spatial selectivity. Critically, this selectivity does not come from the target molecule itself, but from oth ...

. The 2001

Nobel Prize in Chemistry The Nobel Prize in Chemistry () is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outst ...

was awarded to William S. Knowles for his synthesis of L-DOPA from the N-acylacrylate. : L-dopaSyn

References

{{Amino acids Amino acids