Difference between revisions of "Alanine" - New World Encyclopedia
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==Structure== | ==Structure== | ||
| − | In [[biochemistry]], the term | + | In [[biochemistry]], the term [[amino acid]] is frequently used to refer specifically to ''alpha amino acids'': those amino acids in which the amino and carboxylate groups are attached to the same [[carbon]], the so-called α–carbon (alpha carbon). The general structure of these alpha amino acids is: |
''R'' | ''R'' | ||
| Line 28: | Line 28: | ||
where ''R'' represents a ''side chain'' specific to each amino acid. The exception to this basic structure is [[proline]], whose side chain cyclizes onto the backbone, forming a ring structure in which a secondary amino group replaces the primary amino group. | where ''R'' represents a ''side chain'' specific to each amino acid. The exception to this basic structure is [[proline]], whose side chain cyclizes onto the backbone, forming a ring structure in which a secondary amino group replaces the primary amino group. | ||
| − | Most amino acids occur in two possible optical isomers, called D and L. The L amino acids represent the vast majority of amino acids found in [[protein]]s. | + | Most amino acids occur in two possible optical isomers, called D and L. The L amino acids represent the vast majority of amino acids found in [[protein]]s. They are called proteinogenic amino acids. As the name "proteinogenic" (literally, protein building) suggests, these amino acid are encoded by the standard genetic code and participate in the process of protein synthesis. |
| − | + | In alanine, the α-carbon atom is bound with a levorotatory methyl group (-CH<sub>3</sub>), making it one of the simplest α-amino acids with respect to molecular structure (Davidson 2007)and also resulting in alanine being classified as an [[aliphatic compound|aliphatic]] amino acid. The methyl group of alanine is non-reactive and is thus almost never directly involved in protein function. | |
| − | + | ==Sources and biosynthesis== | |
| − | + | Any protein-containing food such as meat, poultry, [[fish]], eggs or dairy products is rich in alanine. [[Racemic]] alanine (equal amounts of left- and right-handed stereoisomers) can be prepared via the addition of [[hydrogen cyanide]] and [[ammonia]] to [[acetaldehyde]] by the Strecker reaction (Kandall and McKenzie 1941). | |
| + | Alanine is most commonly produced in the body by [[reductive amination]] (conversion of a carbonyl group to an amine) of [[pyruvate]]. Because transamination reactions are readily reversible and pyruvate pervasive, alanine can be easily formed and thus has close links to metabolic pathways such as [[glycolysis]], [[gluconeogenesis]], and the [[citric acid cycle]]. | ||
| − | + | Alanine also arises together with lactate from protein via the [[alanine cycle]]. Thus, when muscles produce lactate during times of decreased oxygen, they also produce alanine. This alanine is shuttled to the [[liver]] where it is used to make [[glucose]]. | |
| − | Alanine | + | |
| + | ==Silk== | ||
| + | Alanine is a key component in [[spider]] [[silk]]. | ||
| − | |||
| − | |||
| − | |||
a general trend in spider silk structure is a sequence of amino acids (usually alternating [[glycine]] and [[alanine]], or alanine alone) that [[Molecular self-assembly|self-assemble]] into a [[beta sheet]] conformation. These "Ala rich" blocks are separated by segments of amino acids with bulky side-groups. The beta sheets stack to form [[crystals]], whereas the other segments form [[amorphous]] domains. It is the interplay between the hard crystalline segments, and the elastic semi amorphous regions, that gives spider silk its extraordinary properties. | a general trend in spider silk structure is a sequence of amino acids (usually alternating [[glycine]] and [[alanine]], or alanine alone) that [[Molecular self-assembly|self-assemble]] into a [[beta sheet]] conformation. These "Ala rich" blocks are separated by segments of amino acids with bulky side-groups. The beta sheets stack to form [[crystals]], whereas the other segments form [[amorphous]] domains. It is the interplay between the hard crystalline segments, and the elastic semi amorphous regions, that gives spider silk its extraordinary properties. | ||
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Doolittle RF (1989). "Redundancies in protein sequences" in ''Prediction of Protein Structures and the Principles of Protein Conformation''. (Fasman GD, ed.), pp 599-623, Plenum Press, New York. | Doolittle RF (1989). "Redundancies in protein sequences" in ''Prediction of Protein Structures and the Principles of Protein Conformation''. (Fasman GD, ed.), pp 599-623, Plenum Press, New York. | ||
<references/> | <references/> | ||
| + | |||
| + | .<ref> Kendall, E. C.; McKenzie, B. F. “dl-Alanine” Organic Syntheses, Collected Volume 1, p.21 (1941).http://www.orgsyn.org/orgsyn/pdfs/CV1P0021.pdf</ref> | ||
MB .<ref>{{cite web | author=IUPAC-IUB Joint Commission on Biochemical Nomenclature | title=Nomenclature and Symbolism for Amino Acids and Peptides | work=Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc | url=http://www.chem.qmul.ac.uk/iupac/AminoAcid/ | accessdate=2007-05-17}}</ref> | MB .<ref>{{cite web | author=IUPAC-IUB Joint Commission on Biochemical Nomenclature | title=Nomenclature and Symbolism for Amino Acids and Peptides | work=Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc | url=http://www.chem.qmul.ac.uk/iupac/AminoAcid/ | accessdate=2007-05-17}}</ref> | ||
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[[Category:Proteinogenic amino acids]] | [[Category:Proteinogenic amino acids]] | ||
[[Category:Glucogenic amino acids]] | [[Category:Glucogenic amino acids]] | ||
| − | {{credit|Alanine|137172474|Spider_silk|137474753}} | + | {{credit|Alanine|137172474|Spider_silk|137474753|Alanine_cycle|123826360}} |
[[Category:Life sciences]] | [[Category:Life sciences]] | ||
Revision as of 02:13, 15 June 2007
 
Chemical structure of L-alanine | |
Alanine | |
| Systematic (IUPAC) name | |
| (S)-2-aminopropanoic acid | |
| Identifiers | |
| CAS number | 56-41-7 |
| PubChem | 5950 |
| Chemical data | |
| Formula | C3H7NO2 |
| Mol. weight | 89.1 |
| SMILES | C[C@H](N)C(O)=O |
| Complete data | |
Alanine is an one of the simplest amino acids in terms of molecular structure and one of the most widely found in protein. In humans, the L-isomer, which is the only form that is involved in protein synthesis, is one of the 20 standard amino acids required for normal functioning. However, it is considered to be non-essential since it does not have to be taken in with the diet, but can be synthesized by the human body from other compounds through chemical reactions. It has the chemical formula HO2CCH(NH2)CH3.
Alanine is classified as an nonpolar amino acid. L-alanine is second only to leucine, accounting for 7.8% of the primary structure in a sample of 1,150 proteins (Doolittle 1989). Davidson (2007) reports that it averages about 9% of average protein composition on a per mole basis. Alanine is also involved in the metabolism of tryptophan and the vitamin pyridoxine. Its unique structure makes it one of the principle components of silk, along with glycine, providing the unique characteristics of this natural protein fiber.
The isomer D-alanine occurs in bacterial cell walls and in some peptide antibiotics.
Alanine's three letter code is ala, its one letter code is A, and its codons are GCU, GCC, GCA, and GCG (IUPAC-IUB 1983).
Structure
In biochemistry, the term amino acid is frequently used to refer specifically to alpha amino acids: those amino acids in which the amino and carboxylate groups are attached to the same carbon, the so-called α–carbon (alpha carbon). The general structure of these alpha amino acids is:
R
|
H2N-C-COOH
|
H
where R represents a side chain specific to each amino acid. The exception to this basic structure is proline, whose side chain cyclizes onto the backbone, forming a ring structure in which a secondary amino group replaces the primary amino group.
Most amino acids occur in two possible optical isomers, called D and L. The L amino acids represent the vast majority of amino acids found in proteins. They are called proteinogenic amino acids. As the name "proteinogenic" (literally, protein building) suggests, these amino acid are encoded by the standard genetic code and participate in the process of protein synthesis.
In alanine, the α-carbon atom is bound with a levorotatory methyl group (-CH3), making it one of the simplest α-amino acids with respect to molecular structure (Davidson 2007)and also resulting in alanine being classified as an aliphatic amino acid. The methyl group of alanine is non-reactive and is thus almost never directly involved in protein function.
Sources and biosynthesis
Any protein-containing food such as meat, poultry, fish, eggs or dairy products is rich in alanine. Racemic alanine (equal amounts of left- and right-handed stereoisomers) can be prepared via the addition of hydrogen cyanide and ammonia to acetaldehyde by the Strecker reaction (Kandall and McKenzie 1941).
Alanine is most commonly produced in the body by reductive amination (conversion of a carbonyl group to an amine) of pyruvate. Because transamination reactions are readily reversible and pyruvate pervasive, alanine can be easily formed and thus has close links to metabolic pathways such as glycolysis, gluconeogenesis, and the citric acid cycle.
Alanine also arises together with lactate from protein via the alanine cycle. Thus, when muscles produce lactate during times of decreased oxygen, they also produce alanine. This alanine is shuttled to the liver where it is used to make glucose.
Silk
Alanine is a key component in spider silk.
a general trend in spider silk structure is a sequence of amino acids (usually alternating glycine and alanine, or alanine alone) that self-assemble into a beta sheet conformation. These "Ala rich" blocks are separated by segments of amino acids with bulky side-groups. The beta sheets stack to form crystals, whereas the other segments form amorphous domains. It is the interplay between the hard crystalline segments, and the elastic semi amorphous regions, that gives spider silk its extraordinary properties.
ReferencesISBN links support NWE through referral fees
Doolittle RF (1989). "Redundancies in protein sequences" in Prediction of Protein Structures and the Principles of Protein Conformation. (Fasman GD, ed.), pp 599-623, Plenum Press, New York.
.[1]
MB .[2] INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY and INTERNATIONAL UNION OF BIOCHEMISTRY AND MOLECULAR BIOLOGY IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN)
Nomenclature and Symbolism for Amino Acids and Peptides
(Recommendations 1983)
External links
Template:ChemicalSources
| Major families of biochemicals | ||
| Peptides | Amino acids | Nucleic acids | Carbohydrates | Nucleotide sugars | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides | ||
| Analogues of nucleic acids: | The 20 Common Amino Acids | Analogues of nucleic acids: |
| Alanine (dp) | Arginine (dp) | Asparagine (dp) | Aspartic acid (dp) | Cysteine (dp) | Glutamic acid (dp) | Glutamine (dp) | Glycine (dp) | Histidine (dp) | Isoleucine (dp) | Leucine (dp) | Lysine (dp) | Methionine (dp) | Phenylalanine (dp) | Proline (dp) | Serine (dp) | Threonine (dp) | Tryptophan (dp) | Tyrosine (dp) | Valine (dp) | ||
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- ↑ Kendall, E. C.; McKenzie, B. F. “dl-Alanine” Organic Syntheses, Collected Volume 1, p.21 (1941).http://www.orgsyn.org/orgsyn/pdfs/CV1P0021.pdf
- ↑ IUPAC-IUB Joint Commission on Biochemical Nomenclature. Nomenclature and Symbolism for Amino Acids and Peptides. Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc. Retrieved 2007-05-17.
