4420 L-Phenylalanine Phenylalanine is an essential amino acid and the precursor for the amino acid tyrosine. Like tyrosine, it is the precursor of catecholamines in the body (tyramine, dopamine, epinephrine and norepinephrine). The psychotropic drugs (mescaline, morphine, codeine, and papaverine) also have phenylalanine as a constituent. Phenylalanine is a precursor of the neurotransmitters called catecholamines, which are adrenalin-like substances. Phenylalanine is highly concentrated in the human brain and plasma. Normal metabolism of phenylalanine requires biopterin, iron, niacin, vitamin B6, copper and vitamin C. An average adult ingests 5 g of phenylalanine per day and may optimally need up to 8 g daily. Phenylalanine is highly concentrated in high protein foods, such as meat, cottage cheese and wheat germ. A new dietary source of phenylalanine is artificial sweeteners containing aspartame. Aspartame appears to be nutritious except in hot beverages; however, it should be avoided by phenylketonurics and pregnant women. Phenylketonurics, who have a genetic error of phenylalanine metabolism, have elevated serum plasma levels of phenylalanine up to 400 times normal. Mild phenylketonuria can be an unsuspected cause of hyperactivity, learning problems, and other developmental problems in children. Phenylalanine can be an effective pain reliever. Its use in premenstrual syndrome and Parkinson's may enhance the effects of acupuncture and electric transcutaneous nerve stimulation (TENS). Phenylalanine and tyrosine, like L-dopa, produce a catecholamine effect. Phenylalanine is better absorbed than tyrosine and may cause fewer headaches. Low phenylalanine diets have been prescribed for certain cancers with mixed results. Some tumors use more phenylalanine (particularly melatonin-producing tumors called melanoma). One strategy is to exclude this amino acid from the diet, i.e., a Phenylketonuria (PKU) diet (compliance is a difficult issue; it is hard to quantify and is under-researched). The other strategy is just to increase phenylalanine's competing amino acids, i.e., tryptophan, valine, isoleucine and leucine, but not tyrosine. 63-91-2 6140 C9H11NO2 165.19 White powder. 283 dec°C 2.69E+004 mg/L (at 25°C) Absorbed from the small intestine by a sodium dependent active transport process. Extremely high serum levels of phenylalanine are found in patients with the inborn error of metabolism (IEM) called Phenylketonuria (PKU). At pathological concentrations typical of PKU, phenylalanine self-assembles into fibrils with amyloid-like morphology and well-ordered electron diffraction. These fibrils and their resulting amyloid deposits that localize to the brain appear to be partially responsible for the neural tissue damage seen in PKU patients (A8160). It has also been suggested that very high plasma phenylalanine concentrations can increase phenylalanine entry into brain and thereby restrict the entry of other large neutral amino acids. The lack of large neutral amino acids may lead to disturbed cerebral protein synthesis, which is particularly important for young children (A8162). The mechanism of L-phenylalanine's putative antidepressant activity may be accounted for by its precursor role in the synthesis of the neurotransmitters norepinephrine and dopamine. Elevated brain norepinephrine and dopamine levels are thought to be associated with antidepressant effects. <br/>The mechanism of L-phenylalanine's possible antivitiligo activity is not well understood. It is thought that L-phenylalanine may stimulate the production of melanin in the affected skin. Hepatic. L-phenylalanine that is not metabolized in the liver is distributed via the systemic circulation to the various tissues of the body, where it undergoes metabolic reactions similar to those that take place in the liver. No indication of carcinogenicity to humans (not listed by IARC). L-phenylalanine may be helpful in some with depression. It may also be useful in the treatment of vitiligo. There is some evidence that L-phenylalanine may exacerbate tardive dyskinesia in some schizophrenic patients and in some who have used neuroleptic drugs. Phenylalanine is neurotoxic. Chronic exposure to very high levels of phenylalanine in the blood (as found in phenylketonuria, or PKU) can lead to a build up in the cerebrospinal fluid and brain, leading to seizures, organ damage and unusual posture. High phenylalnine levels are particularly dangerous for children, because it retards brain development and can cause serious learning difficulties. Complications of PKU include severe intellectual disability, brain function abnormalities, microcephaly, mood disorders, irregular motor functioning, and behavioral problems such as attention deficit hyperactivity disorder. Chronically high levels of phenylalanine are associated with at least four other inborn errors of metabolism including: Hartnup Disorder, Hyperphenylalaniemia due to guanosine triphosphate cyclohydrolase deficiency, Tyrosinemia Type 2 (or Richner-Hanhart syndrome) and Tyrosinemia Type 3 (TYRO3). Complications of PKU include severe intellectual disability, brain function abnormalities, microcephaly, mood disorders, irregular motor functioning, and behavioral problems such as attention deficit hyperactivity disorder. If PKU is diagnosed early, an affected newborn can grow up with normal brain development, but only by managing and controlling phenylalanine levels through diet, or a combination of diet and medication. The diet requires severely restricting or eliminating foods high in phenylalanine, such as meat, chicken, fish, eggs, nuts, cheese, legumes, milk and other dairy products. Starchy foods, such as potatoes, bread, pasta, and corn, must be monitored. Optimal health ranges (or "target ranges") of serum phenylalanine are between 120 and 360 µmol/L, and aimed to be achieved during at least the first 10 years of life. Recently it has been found that a chiral isomer of L-phenylalanine (called D-phenylalanine) actually arrests the fibril formation by L-phenylalanine and gives rise to flakes. These flakes do not propagate further and prevent amyloid formation by L-phenylalanine. D-phenylalanine may qualify as a therapeutic molecule in phenylketonuria (A8161). 2014-08-29T06:35:23Z 2026-05-14T16:24:02Z L-Phenylalanine C00079 17295 PHE DB00120 PHE true N[C@@H](CC1=CC=CC=C1)C(O)=O C9H11NO2 InChI=1S/C9H11NO2/c10-8(9(11)12)6-7-4-2-1-3-5-7/h1-5,8H,6,10H2,(H,11,12)/t8-/m0/s1 COLNVLDHVKWLRT-QMMMGPOBSA-N 165.1891 165.078978601 Endogenous Solid -1.38 HMDB00159 CHEMBL301523 5910 <p>Gerald L. Bachman, &#8220;Recovery of L-phenylalanine and L-aspartic acid during preparation of .alpha.-L-aspartyl-L-phenylalanine methyl ester.&#8221; U.S. Patent US4348317, issued January, 1967.</p> CHEM003326 DTXSID001025528 NS00068215 (2S)-2-amino-3-phenylpropanoic acid 63.31999999999999 45.11630000000001 17.0319763846329 3 3 2 2.469229772182635 9.446936344396194 0 1 -1.35 -1.60 4.14e+00 g/l