organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J. ...

, an imino acid is any molecule that contains both

imine In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bon ...

(>C=NH) and

carboxyl In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxyli ...

(-C(=O)-OH)

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...

s. Imino acids are structurally related to

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...

, which have

amino In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such ...

group instead of imine—a difference of single vs double-bond between nitrogen and carbon. The simplest example is dehydroglycine. D-Amino acid oxidase is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. ...

that is able to convert amino acids into imino acids. Also the direct biosynthetic precursor to the amino acid

proline Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group but is rather a secondary amine. The secondary amine nitrogen is in the pro ...

is the imino acid (''S'')-Δ¹-pyrroline-5-carboxylate (P5C).

Related terminology

Secondary amino acids, amino acids containing a secondary amine group are sometimes named imino acids, though this usage is obsolescent. The only

proteinogenic amino acid Proteinogenic amino acids are amino acids that are incorporated biosynthetically into proteins during translation. The word "proteinogenic" means "protein creating". Throughout known life, there are 22 genetically encoded (proteinogenic) amino a ...

of this type is

, although the related

non-proteinogenic amino acids In biochemistry, non-coded or non-proteinogenic amino acids are distinct from the 22 proteinogenic amino acids (21 in eukaryotesplus formylmethionine in eukaryotes with prokaryote organelles like mitochondria) which are naturally encoded in the ...

hydroxyproline (2''S'',4''R'')-4-Hydroxyproline, or L-hydroxyproline ( C5 H9 O3 N), is an amino acid, abbreviated as Hyp or O, ''e.g.'', in Protein Data Bank. Structure and discovery In 1902, Hermann Emil Fischer isolated hydroxyproline from hydrolyzed gelatin. ...

and

pipecolic acid Pipecolic acid (piperidine-2-carboxylic acid) is an organic compound with the formula HNC5H9CO2H. It is a carboxylic acid derivative of piperidine and, as such, an amino acid, although not one encoded genetically. Like many other α-amino acids, p ...

have often been included in studies of this class of compounds. The term ''imino acid'' is also the obsolete term for '' imidic acids'', structures containing the -C(=NH)-OH group, and should not be used for them.

References

External links

* Carboxylic acids {{Amino acids