In organic chemistry, secondary amino acids are amino acids which do not contain the amino group −NH2 but is rather a secondary amine (>NH). Secondary amino acids can be classified to cyclic acids, such as proline, and acyclic N-substituted amino acids.[1][2]

In nature, proline, hydroxyproline, pipecolic acid and sarcosine are well-known secondary amino acids. Proline is the only proteinogenic secondary amino acids. Other secondary amino acids are non-proteinogenic amino acids. In protein, hydroxyproline is incorporated into protein by hydroxylation of proline. Pipecolic acid, a heavier analog of proline, is found in efrapeptin. Sarcosine is a N-methylized glycine so its methyl group is used in many biochemical reactions. Azetidine-2-carboxylic acid, which is a smaller homolog of proline in plants.

Properties

Proline and its higher homolog pipecolic acid affect the secondary structure of protein. D-alpha-amino acid - L-alpha-amino acid sequence can induce beta hairpin.[1] It suggested that acyclic secondary amino acids are more flexible than cyclic secondary amino acids in protein by replacement of pipecolic acid by N-methyl-L-alanine in efrapeptin C.[1]

Ninhydrin tests of proline and hydroxyproline give yellow results.

In enzymology, a N-methyl-L-amino-acid oxidase is an oxidase of a subtype of secondary amino acids.

See also

References

  1. ^ a b c Konar AD, Vass E, Hollósi M, Majer Z, Grüber G, Frese K, Sewald N (2013). "Conformational Properties of Secondary Amino Acids: Replacement of Pipecolic Acid by N-Methyl-L-alanine in Efrapeptin C". Chemistry & Biodiversity. 10 (5): 942–951. doi:10.1002/cbdv.201300086. PMID 23681735. S2CID 37926505.
  2. ^ V V Ryakhovskii; S V Agafonov; Yu M Kosyrev (1991). "Special features of the synthesis of peptides containing secondary amino acids". Russ. Chem. Rev. 60 (8): 924–933. Bibcode:1991RuCRv..60..924R. doi:10.1070/RC1991v060n08ABEH001119. S2CID 250735186.

External links

Encoded (proteinogenic) amino acids
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