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EspañolPHENYLALANINE
:'''Phe' redirects here. For the BitTorrent feature, see PHE. For the constellation, see Phoenix (constellation).''
'Phenylalanine' is an α-amino acid with the formula HO2CCH(NH2)CH2C6H5. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. The codons for L-phenylalanine are UUU and UUC. It is a white, powdery solid. L-Phenylalanine (LPA) is an electrically-neutral amino acid, one of the twenty common amino acids used to biochemically form proteins, coded for by DNA.
Phenylalanine cannot be made by animals, which have to obtain it from their diet. It is produced by plants and most microorganisms from prephenate, an intermediate on the shikimate pathway.Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
Prephenate is decarboxylated with loss of the hydroxyl group to give phenylpyruvate. This species is transaminated using glutamate as the nitrogen source to give phenylalanine and α-ketoglutarate.
L-phenylalanine can also be converted into L-tyrosine, another one of the DNA-encoded amino acids. L-tyrosine in turn is converted into L-DOPA, which is further converted into dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline) (the latter three are known as the catecholamines).
Phenylalanine uses the same active transport channel as tryptophan to cross the blood-brain barrier, and, in large quantities, interferes with the production of serotonin.
Lignin is derived from phenylalanine and from tyrosine. Phenylalanine is converted to cinnamic acid by the enzyme phenylalanine ammonia lyase.
Main articles: Phenylketonuria
The genetic disorder phenylketonuria (PKU) is the inability to metabolize phenylalanine. Individuals with this disorder are known as "phenylketonurics" and must abstain from consumption of phenylalanine. This dietary restriction also applies to pregnant women with hyperphenylalanine (high levels of phenylalanine in blood) because they do not properly metabolize the amino acid phenylalanine. Phenylalanine is present in many sugarless gums, Monster Munch crisps, sugarless soft drinks (such as diet sodas including CocaCola Zero), some forms of Lipton Tea, Icebreakers Mints, Clear Splash flavored water, and a number of other food products, all of which must be labeled: "Phenylketonurics: Contains phenylalanine." (In the UK, foods containing aspartame must carry ingredients panels that refer to the presence of 'aspartame or E951', says the country's Food Standards Agency [1] - and they 'must be labeled with a warning "Contains a source of phenylalanine".' This is usually the last line of the ingredients. 'Products containing sweeteners such as aspartame must show the statement "with sweetener(s)",' the agency adds. This should be 'close to the main product name'. And 'foods that contain both sugar and sweetener must carry the statement "with sugar and sweetener(s)". In addition, foods that contain aspartame must be labeled with a warning 'contains a source of phenylalanine'. This warning is specifically to aid individuals who suffer from PKU, so that they can avoid such foods.')
Phenylalanine itself is not present in the food. Rather, the artificial sweetener sold under the names "Equal" and "NutraSweet" contain aspartame, an ester that is hydrolyzed in the body to give phenylalanine, aspartic acid, and methanol (wood alcohol). Thus, aspartame is problematic for persons with PKU. The amounts produced by aspartame pose a risk however, as far larger quantities of the amino acid would be obtained through consuming normal protein. Interestingly, the macaque genome was recently sequenced and it was found that macaques naturally have a mutation that is found in humans who have PKU.[2]
D-phenylalanine (DPA) either as a single enantiomer or as a component of the racemic mixture is available through conventional organic synthesis. It does not participate in protein biosynthesis although it is found in proteins, in small amounts, particularly aged proteins and food proteins that have been processed. The biological functions of D-amino acids remain unclear. Some D-amino acids, such as D-phenylalanine, may have pharmacological activity.
DL-Phenylalanine is marketed as a nutritional supplement for its putative analgesic and antidepressant activities. The putative analgesic activity of DL-phenylalanine may be explained by the possible blockage by D-phenylalanine of enkephalin degradation by the enzyme carboxypeptidase A. The mechanism of DL-phenylalanine's putative antidepressant activity may be accounted for by the precursor role of L-phenylalanine in the synthesis of the neurotransmitters norepinephrine and dopamine. Elevated brain norepinephrine and dopamine levels are thought to be associated with antidepressant effects.
D-phenylalanine is absorbed from the small intestine, following ingestion, and transported to the liver via the portal circulation. A fraction of D-phenylalanine appears to be converted to L-phenylalanine. D-phenylalanine is distributed to the various tissues of the body via the systemic circulation. D-phenylalanine appears to cross the blood-brain barrier with less efficiency than L-phenylalanine. A fraction of an ingested dose of D-phenylalanine is excreted in the urine.
The genetic codon for phenylalanine was the first to be discovered. Marshall W. Nirenberg discovered that insertion of ''m''-RNA made up of multiple uracil repeats into ''E. coli'', the bacterium produced a new protein, made up solely of repeated phenylalanine amino acids.
★ Phenylalanine and tyrosine biosynthesis
★ Computational Chemistry Wiki
★ Nitrogen Order's Molecule of the Week
★ DL-phenylalanine versus imipramine in depression
| 'Phenylalanine' | |
|---|---|
| Systematic name | 2-Amino-3-phenyl- propanoic acid |
| Abbreviations | Phe F |
| Chemical formula | C9H11NO2 |
| Molecular mass | 165.19 g mol-1 |
| Melting point | 283 °C |
| Density | 1.29 g cm-3 |
| Isoelectric point | 5.5 |
| p''K''a | 2.20 9.09 |
| PubChem | 994 |
| CAS number | ★ [673-06-3] (D) ★ [63-91-2] (L) ★ [150-30-1] (D/L or racemic) |
| SMILES | |
 Chemical structure of Phenylalanine  Chemical structure of Phenylalanine | |
'Phenylalanine' is an α-amino acid with the formula HO2CCH(NH2)CH2C6H5. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. The codons for L-phenylalanine are UUU and UUC. It is a white, powdery solid. L-Phenylalanine (LPA) is an electrically-neutral amino acid, one of the twenty common amino acids used to biochemically form proteins, coded for by DNA.
| Contents |
| Biosynthesis |
| Other biological roles |
| Phenylketonuria |
| D- and DL-phenylalanine |
| History |
| References |
| External links |
Biosynthesis
Phenylalanine cannot be made by animals, which have to obtain it from their diet. It is produced by plants and most microorganisms from prephenate, an intermediate on the shikimate pathway.Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
Prephenate is decarboxylated with loss of the hydroxyl group to give phenylpyruvate. This species is transaminated using glutamate as the nitrogen source to give phenylalanine and α-ketoglutarate.
Other biological roles
L-phenylalanine can also be converted into L-tyrosine, another one of the DNA-encoded amino acids. L-tyrosine in turn is converted into L-DOPA, which is further converted into dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline) (the latter three are known as the catecholamines).
Phenylalanine uses the same active transport channel as tryptophan to cross the blood-brain barrier, and, in large quantities, interferes with the production of serotonin.
DLPA RXN.GIF
Lignin is derived from phenylalanine and from tyrosine. Phenylalanine is converted to cinnamic acid by the enzyme phenylalanine ammonia lyase.
Phenylketonuria
Main articles: Phenylketonuria
The genetic disorder phenylketonuria (PKU) is the inability to metabolize phenylalanine. Individuals with this disorder are known as "phenylketonurics" and must abstain from consumption of phenylalanine. This dietary restriction also applies to pregnant women with hyperphenylalanine (high levels of phenylalanine in blood) because they do not properly metabolize the amino acid phenylalanine. Phenylalanine is present in many sugarless gums, Monster Munch crisps, sugarless soft drinks (such as diet sodas including CocaCola Zero), some forms of Lipton Tea, Icebreakers Mints, Clear Splash flavored water, and a number of other food products, all of which must be labeled: "Phenylketonurics: Contains phenylalanine." (In the UK, foods containing aspartame must carry ingredients panels that refer to the presence of 'aspartame or E951', says the country's Food Standards Agency [1] - and they 'must be labeled with a warning "Contains a source of phenylalanine".' This is usually the last line of the ingredients. 'Products containing sweeteners such as aspartame must show the statement "with sweetener(s)",' the agency adds. This should be 'close to the main product name'. And 'foods that contain both sugar and sweetener must carry the statement "with sugar and sweetener(s)". In addition, foods that contain aspartame must be labeled with a warning 'contains a source of phenylalanine'. This warning is specifically to aid individuals who suffer from PKU, so that they can avoid such foods.')
Phenylalanine itself is not present in the food. Rather, the artificial sweetener sold under the names "Equal" and "NutraSweet" contain aspartame, an ester that is hydrolyzed in the body to give phenylalanine, aspartic acid, and methanol (wood alcohol). Thus, aspartame is problematic for persons with PKU. The amounts produced by aspartame pose a risk however, as far larger quantities of the amino acid would be obtained through consuming normal protein. Interestingly, the macaque genome was recently sequenced and it was found that macaques naturally have a mutation that is found in humans who have PKU.[2]
D- and DL-phenylalanine
D-phenylalanine (DPA) either as a single enantiomer or as a component of the racemic mixture is available through conventional organic synthesis. It does not participate in protein biosynthesis although it is found in proteins, in small amounts, particularly aged proteins and food proteins that have been processed. The biological functions of D-amino acids remain unclear. Some D-amino acids, such as D-phenylalanine, may have pharmacological activity.
DL-Phenylalanine is marketed as a nutritional supplement for its putative analgesic and antidepressant activities. The putative analgesic activity of DL-phenylalanine may be explained by the possible blockage by D-phenylalanine of enkephalin degradation by the enzyme carboxypeptidase A. The mechanism of DL-phenylalanine's putative antidepressant activity may be accounted for by the precursor role of L-phenylalanine in the synthesis of the neurotransmitters norepinephrine and dopamine. Elevated brain norepinephrine and dopamine levels are thought to be associated with antidepressant effects.
D-phenylalanine is absorbed from the small intestine, following ingestion, and transported to the liver via the portal circulation. A fraction of D-phenylalanine appears to be converted to L-phenylalanine. D-phenylalanine is distributed to the various tissues of the body via the systemic circulation. D-phenylalanine appears to cross the blood-brain barrier with less efficiency than L-phenylalanine. A fraction of an ingested dose of D-phenylalanine is excreted in the urine.
History
The genetic codon for phenylalanine was the first to be discovered. Marshall W. Nirenberg discovered that insertion of ''m''-RNA made up of multiple uracil repeats into ''E. coli'', the bacterium produced a new protein, made up solely of repeated phenylalanine amino acids.
References
External links
★ Phenylalanine and tyrosine biosynthesis
★ Computational Chemistry Wiki
★ Nitrogen Order's Molecule of the Week
★ DL-phenylalanine versus imipramine in depression
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