Alanine

Source: Wikipedia, the free encyclopedia.
Not to be confused with the chemical compound Allantoin, or the phenyl compound Aniline.
Alanine
Alanine in non-ionic form
Skeletal formula of L-alanine (neutral form)
Ball-and-stick model (zwitterionic form)
Space-filling model (zwitterionic form)
Names
IUPAC name
Alanine[1]
Systematic IUPAC name
2-Aminopropanoic acid
Other names
Alanic acid
Alaninic acid
2-Aminopropionic acid
Identifiers
3D model (
JSmol
)
3DMet
1720248
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard
 100.000.249 Edit this at Wikidata
EC Number
  • L: 206-126-4
49628
IUPHAR/BPS
KEGG
UNII
  • InChI=1S/C3H7NO2/c1-2(4)3(5)6/h2H,4H2,1H3,(H,5,6)/t2-/m0/s1
    Key: QNAYBMKLOCPYGJ-REOHCLBHSA-N checkY
  • D/L: Key: QNAYBMKLOCPYGJ-UHFFFAOYSA-N
  • D: Key: QNAYBMKLOCPYGJ-UWTATZPHSA-N
  • L: C[C@@H](C(=O)O)N
  • D: C[C@H](C(=O)O)N
  • L Zwitterion: C[C@@H](C(=O)[O-])[NH3+]
  • D Zwitterion: C[C@H](C(=O)[O-])[NH3+]
Properties
C3H7NO2
Molar mass 89.094 g·mol−1
Appearance white powder
Density 1.424 g/cm3
Melting point 258 °C (496 °F; 531 K) (sublimes)
167.2 g/L (25 °C)
log P -0.68[2]
Acidity (pKa)
  • 2.34 (carboxyl; H2O)
  • 9.87 (amino; H2O)[3]
-50.5·10−6 cm3/mol
Supplementary data page
Alanine (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Alanine (symbol Ala or A),

codons starting with GC (GCU, GCC, GCA
, and GCG).

The L-

peptide antibiotics, and occurs in the tissues of many crustaceans and molluscs as an osmolyte.[7]

History and etymology

Alanine was first synthesized in 1850 when Adolph Strecker combined acetaldehyde and ammonia with hydrogen cyanide.[8][9][10] The amino acid was named Alanin in German, in reference to aldehyde, with the interfix -an- for ease of pronunciation,[11] the German ending -in used in chemical compounds being analogous to English -ine.

Structure

Alanine is an

methyl group (-CH3). Alanine is the simplest α-amino acid after glycine. The methyl side-chain of alanine is non-reactive and is therefore hardly ever directly involved in protein function.[12] Alanine is a nonessential amino acid
, meaning it can be manufactured by the human body, and does not need to be obtained through the diet. Alanine is found in a wide variety of foods, but is particularly concentrated in meats.

Sources

Biosynthesis

Alanine can be synthesized from

branched chain amino acids such as valine, leucine, and isoleucine
.

Alanine is produced by

reducing equivalent.[6]: 721  Because transamination reactions are readily reversible and pyruvate is present in all cells, alanine can be easily formed and thus has close links to metabolic pathways such as glycolysis, gluconeogenesis, and the citric acid cycle.[13]

Chemical synthesis

See also: Hell–Volhard–Zelinsky halogenation

L-Alanine is produced industrially by decarboxylation of

L-aspartate by the action of aspartate 4-decarboxylase. Fermentation routes to L-alanine are complicated by alanine racemase.[14]

Racemic alanine can be prepared by the condensation of acetaldehyde with ammonium chloride in the presence of sodium cyanide by the Strecker reaction,[15] or by the ammonolysis of 2-bromopropanoic acid.[16]

Degradation

Alanine is broken down by oxidative deamination, the inverse reaction of the reductive amination reaction described above, catalyzed by the same enzymes. The direction of the process is largely controlled by the relative concentration of the substrates and products of the reactions involved.[6]: 721 

Alanine World Hypothesis

Alanine is one of the twenty canonical α-amino acids used as building blocks (monomers) for the ribosome-mediated biosynthesis of proteins. Alanine is believed to be one of the earliest amino acids to be included in the genetic code standard repertoire.[17][18][19][20] On the basis of this fact the "Alanine World" hypothesis was proposed.

secondary structural elements. Dominant secondary structures in life as we know it are α-helices and β-sheets and most canonical amino acids can be regarded as chemical derivatives of Alanine. Therefore, most canonical amino acids in proteins can be exchanged with Ala by point mutations while the secondary structure remains intact. The fact that Ala mimics the secondary structure preferences of the majority of the encoded amino acids is practically exploited in alanine scanning mutagenesis. In addition, classical X-ray crystallography often employs the polyalanine-backbone model[22] to determine three-dimensional structures of proteins using molecular replacement - a model-based phasing
method.

Physiological function

Glucose–alanine cycle

In mammals, alanine plays a key role in

ammonium, which in turn participates in the urea cycle to form urea which is excreted through the kidneys.[23]

The glucose–alanine cycle enables pyruvate and glutamate to be removed from muscle and safely transported to the liver. Once there, pyruvate is used to regenerate glucose, after which the glucose returns to muscle to be metabolized for energy: this moves the energetic burden of gluconeogenesis to the liver instead of the muscle, and all available ATP in the muscle can be devoted to muscle contraction.[23] It is a catabolic pathway, and relies upon protein breakdown in the muscle tissue. Whether and to what extent it occurs in non-mammals is unclear.[24][25]

Link to diabetes

Alterations in the alanine cycle that increase the levels of serum

alanine aminotransferase (ALT) are linked to the development of type II diabetes.[26]

Chemical properties

(S)-Alanine (left) and (R)-alanine (right) in zwitterionic form at neutral pH

Alanine is useful in loss of function experiments with respect to phosphorylation. Some techniques involve creating a library of genes, each of which has a point mutation at a different position in the area of interest, sometimes even every position in the whole gene: this is called "scanning mutagenesis". The simplest method, and the first to have been used, is so-called alanine scanning, where every position in turn is mutated to alanine.[27]

Hydrogenation of alanine gives the

amino alcohol alaninol
, which is a useful chiral building block.

Free radical

The deamination of an alanine molecule produces the free radical CH3C•HCO2−. Deamination can be induced in solid or aqueous alanine by radiation that causes homolytic cleavage of the carbon–nitrogen bond.[28]

This property of alanine is used in

radiotherapy. When normal alanine is irradiated, the radiation causes certain alanine molecules to become free radicals, and, as these radicals are stable, the free radical content can later be measured by electron paramagnetic resonance in order to find out how much radiation the alanine was exposed to.[29] This is considered to be a biologically relevant measure of the amount of radiation damage that living tissue would suffer under the same radiation exposure.[29] Radiotherapy treatment plans can be delivered in test mode to alanine pellets, which can then be measured to check that the intended pattern of radiation dose is correctly delivered by the treatment system.[30]

References

  1. ISBN 978-0-85404-182-4
    .
  2. ^ "L-alanine MSDS". ChemSrc.
  3. ISBN 978-1-4987-5428-6
    .
  4. IUPAC-IUB Joint Commission on Biochemical Nomenclature. 1983. Archived from the original
    on 9 October 2008. Retrieved 5 March 2018.
  5. ISBN 978-0-306-43131-9
    .
  6. ^
    OCLC 42290721
    .
  7. ISBN 978-4-431-56077-7
    .
  8. doi:10.1002/jlac.18500750103
    . Strecker names alanine on p. 30.
  9. doi:10.1002/jlac.18540910309
    .
  10. ^ "Alanine". AminoAcidsGuide.com. 10 June 2018. Retrieved 14 April 2019.
  11. ^ "Alanine". Oxford Dictionaries. Archived from the original on December 24, 2014. Retrieved 2015-12-06.
  12. ISBN 978-0-07-107007-2
    .
  13. PMID 31082163
    , retrieved 2023-07-09
  14. ISBN 978-3527306732
    .
  15. doi:10.15227/orgsyn.009.0004
    ; Collected Volumes, vol. 1, p. 21..
  16. doi:10.15227/orgsyn.009.0004
    ; Collected Volumes, vol. 1, p. 21.
  17. PMID 11164045
    .
  18. S2CID 9039622
    .
  19. PMID 31694194
    .
  20. PMID 31504783
    .
  21. PMID 31279217
    .
  22. PMID 19171966
    .
  23. ^
    ISBN 0-7167-4339-6
    ..
  24. ISBN 978-0-08-049751-8
    .
  25. ISBN 978-0-8493-8411-0
    .
  26. PMID 15504965
    .
  27. ISBN 978-1-4200-7659-2
    .
  28. S2CID 97855573
    ..
  29. ^
    OCLC 990023546
    .
  30. PMID 35474242
    .
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