What is "dehydroamino acid"

n. (context organic chemistry English) Any derivative of an amino acid that has formally lost two hydrogen atoms to form a double bond

In biochemistry, a dehydroamino acid is an amino acids with a C=C double bond in its side chain. Dehydroamino acids are not coded by DNA, but arise via post-transcriptional modification. The most common examples are dehydroalanine and dehydrobutyrine, derived from dehydration of serine/ cysteine and threonine, respectively.

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.