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
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 am ...
, which have
amino 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 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 prot ...
is the imino acid (''S'')-Δ
1-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 of this type is
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 prot ...
, although the related
non-proteinogenic amino acids hydroxyproline and
pipecolic acid have often been included in studies of this class of compounds.
The term ''imino acid'' is also the obsolete term for ''
imidic acid
In chemistry, an imidic acid is any molecule that contains the -C(=NH)-OH functional group. It is the tautomer of an amide and the isomer of an oxime.
The term "imino acid" is an obsolete term for this group that should not be used in this contex ...
s'', structures containing the -C(=NH)-OH group, and should not be used for them.
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References
External links
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Carboxylic acids
{{Amino acids