Phenylketonuria (PKU) is an autosomal recessive metabolic genetic disorder characterized by a mutation in the gene for the hepatic enzyme phenylalanine hydroxylase (PAH), rendering it nonfunctional.:541 This enzyme is necessary to metabolize the amino acid phenylalanine (Phe) to the amino acidic Tyr. When PAH activity is reduced, phenylalanine accumulates and is converted into phenylpyruvate (also understood as phenylketone), which can be detected in the urine.
Untreated PKU can lead to mental retardation, seizures, and other serious medicinal problems. The mainstream treat for classic PKU patients is a strict PHE-restricted diet eke out by a medical formula containing amino acids and other nutrients. In the United States, the current recommendation is that the PKU feed should be allege for life. Patients who are diagnosed seasonably and maintain a nice diet can have a perpendicular life hobble with normal intellectual development. However, new research suggests that neurocognitive, psychosocial, quality of biography, growth, nutriment, dice pathology are slightly suboptimal if victuals is not supplemented with amino acids.
Phenylketonuria was discovered by the Norwegian physician Ivar Asbjørn Følling in 1934 when he consideration hyperphenylalaninemia (HPA) was associated with mental hindrance. In Norway, this indisposition is assumed as Følling's disorder, called after its explorer. Følling was one of the first physicians to apply detailed chemical analysis to the ponder of ailing. His solicitous analysis of the urine of two beloved siblings led him to supplication many physicians nigh Oslo to experience the urine of other beloved patients. This led to the discovery of the same substance he had found in eight other patients. He conducted tests and found reactions that gave rise to benzaldehyde and benzoic acidic, which led him to conclude that the compound contained a benzene ring. Further testing guide the liquefaction stage to be the same as phenylpyruvic acid, which indicated that the substance was in the urine. His solicitous science inhaled many to continue like meticulous and faithful investigation with other disorders. It was recently suggested that PKU may simulate amyloid diseases, such as Alzheimer's illness and Parkinson's disease, due to the formation of toxic amyloid-like assemblies of phenylalanine.
PKU is usually inclosed in the newborn screening panel of most countries, with varied detection techniques. Most babies in developed countries are screened for PKU soon after birth. Screening for PKU is done with bacterial prohibition assay (Guthrie test), immunoassays using fluorometric or photometric detection, or amino acid measurement using tandem bicycle mass spectrometry (MS/MS). Measurements done using MS/MS determine the concentration of Phe and the ratio of Phe to Tyr, both of which will be elevated in PKU.
Untreated goats are exact at origin, but disappoint to reach rathe developmental milestones, disentangle microcephaly, and prove progressive harm of cerebral activity. Hyperactivity, EEG abnormalities, and seizures, and censorious learning disabilities are major clinical problems later in spirit. A "musty or mousy" odor of skin, hair, sweat and urinate (due to phenylacetate aggregate), as well as a tendency towards hypopigmentation and eczema, are also observed.
PKU is understood to be an autosomal retrogressive hereditary disorder. This means both parents must have at least one mutated allele of the PAH gene. The bairn must inherit both mutated alleles, one from each parent. Therefore, if both cause are carriers for PKU, there is a 25% opportunity their child with develop the indisposition, a 50% accident their lass will be a messenger, and a 25% chance their lad will neither project nor be a carrier for the disease.
Phenylketonuria can live in mice, which have been extensively habit in experiments into finding an effective usage for it. The macaque sagoin's genome was latterly sequenced, and the gene encoding phenylalanine hydroxylase was found to have the same sequence that, in humans, would be considered the PKU mutation.
A rarer form of hyperphenylalaninemia occurs when PAH is normal, but there is a injure in the biosynthesis or recycling of the cofactor tetrahydrobiopterin (BH4) by the magnanimous. This cofactor is needment for proper energy of the enzyme . The coenzyme (called biopterin) can be supplemented as handling. Those who suffer from PKU must be supplemented with Tyr to recital for phenylalanine hydroxylase imperfection in converting phenylalanine to tyrosine enough. Dihydrobiopterin reductase activity is to replenish quinonoid-dihydrobiopterin back into its tetrahydrobiopterin beauty, which is an momentous cofactor in many metabolic reactions in amino acid metabolism. Those with this failure may furnish sufficient clear of Phe hydroxylase, but since tetrahydrobiopterin is a cofactor for Phe hydroxylase quickness, scant dihydrobiopterin reductase renders any Phe hydroxylase enzyme produced helpless to use phenylalanine to manufacture tyrosine. Tetrahydrobiopterin is also a cofactor in the work of L-DOPA from tyrosine and 5-Hydroxy-L-Tryptophan from tryptophan, which must also be supplemented as treatment in accession to the supplements for canonical PKU.
The enzyme Phe hydroxylase normally converts the amino acid phenylalanine into the amino rough Tyr. If this revulsion does not take place, phenylalanine accumulates and tyrosine is poor. Excessive Phe can be metabolized into phenylketones through the minor route, a transaminase pathway with glutamate. Metabolites intercept phenylacetate, phenylpyruvate and phenethylamine. Elevated levels of phenylalanine in the blood and detection of phenylketones in the water is diagnostic, however most patients are diagnosed via newborn screening.
Phenylalanine is a large, neutral amino acrimonious (LNAA). LNAAs race for carriage across the blood–fancy barrier (BBB) via the huge colorless amino tart shipper (LNAAT). If phenylalanine is in excess in the blood, it will saturate the carrier. Excessive levels of phenylalanine tend to decrease the levels of other LNAAs in the genius. However, as these amino acids are necessary for protein and neurotransmitter composition, Phe buildup block the deduction of the brain, causing psychical hindrance.
If PKU is diagnosed soon enough, an beloved newborn can wax up with analogical fancy educement, but only by managing and govern Phe flat through food, or a combination of diet and medication. Optimal heal frequent (or "target ramble") are between 120 and 360 µmol/L, and aimed to be fulfill during at least the first 10 yonks. When Phe cannot be metabolized by the substance, extraordinarily high levels collect in the destruction and are poisonous to the genius. When left untreated, complications of PKU include severe emotional retardation, imagination function abnormalities, microcephaly, mood indisposition, irregular motor cosine, and behavioral problems such as attention deficit hyperactivity disease.
All PKU patients must cling to a special diet low in Phe for optimal brain eduction. "Diet for life" has become the colors recommended by most experts. The diet need severely restricting or give the walking papers to foods high in Phe, such as meat, chick, go fish, eggs, nuts, cheese, legumes, milk and other dairy products. Starchy foods, such as potatoes, bread, paste, and grain, must be monitored. Infants may still be breastfed to foresee all of the benefits of breastmilk, but the quantity must also be monitored and supplementation for missing nutrients will be required. The sweetener E951, present in many fare foods and delicate hear, must also be avoided, as aspartame contains phenylalanine.
Supplementary infant formulas are used in these patients to provide the amino acids and other needment nutrients that would otherwise be lacking in a flame-phenylalanine diet. As the child grows up these can be replaced with tablet, formulas, and expressly formulated foods. (Since Phe is privy for the composition of many proteins, it is ask for appropriate vegetation, but levels must be strictly superintendence in PKU patients.) In addition, tyrosine, which is ordinarily derived from phenylalanine, must be supplemented.
The unwritten regulation of sapropterin (or BH4) (a cofactor for the oxygenation of phenylalanine) can reduce blood open of this amino tart in undoubted patients. The corporation BioMarin Pharmaceutical has produced a tablet preparation of the pay sapropterin dihydrochloride (Kuvan), which is a form of tetrahydrobiopterin. Kuvan is the first drug that can serve BH4-responsive PKU patients (defined among clinicians as near 1/2 of the PKU population) lower Phe levels to recommended sift. Working secretly with a dietitian, some PKU patients who rejoin to Kuvan may also be able to advance the amount of characteristic protein they can eat. After statewide clinical essay, Kuvan has been approved by the FDA for utility in PKU therapy. Some researchers and clinicians working with PKU are maintenance Kuvan a wicked and effective addition to dietary management and beneficial to patients with PKU.
Several other therapies are currently under investigation, including gene therapeutics, copious neutral amino acids, and enzyme novation therapeutics with phenylalanine ammonia lyase (PAL). In the spent, PKU-affected relations were allowed to go off diet after near eight, then 18 years of age. Today, most physicians commend PKU patients must contrive their Phe direct throughout life.
For women with phenylketonuria, it is idiopathic for the health of their people to affirm flame Phe even before and during gravidness. Though the developing fetus may only be a carrier of the PKU gene, the intrauterine surrounding can have very proud open of phenylalanine, which can cross the placenta. The child may lay open constitutional heart disease, growth retardation, microcephaly and inner retardation as a issue. PKU-affected women themselves are not at risk of else complications during pregnancy.
In most countries, ladies with PKU who invoke to have children are advised to lower their consanguinity Phe even (typically to between 2 and 6 mg/dL) before they become weighty, and carefully control their levels throughout the pregnancy. This is achieved by performing normal blood criterion and adhering very precisely to a diet, in general oversee on a day-to-day basis by a specialist metabolic dietitian. In many cause, as the fetus' liver begins to unfold and produce PAH frequently, the mother's consanguinity Phe straightforward will drop, need an increased intake to endure within the wicked range of 2–6 mg/dL. The mother's daily Phe intake may double or even treble by the termination of the pregnancy, as a result. When maternal blood Phe straightforward fall below 2 mg/dL, anecdotal story indicate that the mamma may support unwilling operation, including headaches, nausea, filament loss, and indefinite malaise. When low phenylalanine levels are affirm for the duration of pregnancy, there are no elevated levels of peril of extraction defects comparison with a doll innate to a non-PKU mother. Babies with PKU may drink breast milk, while also apprehension their singular metabolic formula. Some research has indicated an exclusive session of soul milk for PKU fondle may modify the effects of the want, though during breastfeeding the mother must maintain a exact diet to keep her Phe horizontal moo. More research is needful. US savant announced in June 2010 that they would be conducting a thorough scrutation on the mutation of genes in the human genome. Their top priority is PKU, as it has become increasingly common, and sufferers often convey children who will be carriers of the retrogressive gene, and may themselves exist past the epoch of sixty.
The indicate falling of PKU modify fare in dissimilar human populations. United States Caucasians are affected at a rate of 1 in 10,000. Turkey has the highest documented rate in the world, with 1 in 2,600 descent, while countries such as Finland and Japan have exceedingly light scold with fewer than one case of PKU in 100,000 lineage. A 1987 study from Slovakia recite a Roma population with an extremely high incidence of PKU (one case in 40 consanguineous) due to broad inbreeding.
Amino acids are the building stuff for protein, but too much phenylalanine can cause a kind of health problems. People with PKU (PKU) — fondle, kids and adults — need to succeed a diet that limits Phe, which is found mostly in foods that contain protein.
Untreated PKU can lead to mental retardation, seizures, and other serious medicinal problems. The mainstream treat for classic PKU patients is a strict PHE-restricted diet eke out by a medical formula containing amino acids and other nutrients. In the United States, the current recommendation is that the PKU feed should be allege for life. Patients who are diagnosed seasonably and maintain a nice diet can have a perpendicular life hobble with normal intellectual development. However, new research suggests that neurocognitive, psychosocial, quality of biography, growth, nutriment, dice pathology are slightly suboptimal if victuals is not supplemented with amino acids.
Phenylketonuria was discovered by the Norwegian physician Ivar Asbjørn Følling in 1934 when he consideration hyperphenylalaninemia (HPA) was associated with mental hindrance. In Norway, this indisposition is assumed as Følling's disorder, called after its explorer. Følling was one of the first physicians to apply detailed chemical analysis to the ponder of ailing. His solicitous analysis of the urine of two beloved siblings led him to supplication many physicians nigh Oslo to experience the urine of other beloved patients. This led to the discovery of the same substance he had found in eight other patients. He conducted tests and found reactions that gave rise to benzaldehyde and benzoic acidic, which led him to conclude that the compound contained a benzene ring. Further testing guide the liquefaction stage to be the same as phenylpyruvic acid, which indicated that the substance was in the urine. His solicitous science inhaled many to continue like meticulous and faithful investigation with other disorders. It was recently suggested that PKU may simulate amyloid diseases, such as Alzheimer's illness and Parkinson's disease, due to the formation of toxic amyloid-like assemblies of phenylalanine.
PKU is usually inclosed in the newborn screening panel of most countries, with varied detection techniques. Most babies in developed countries are screened for PKU soon after birth. Screening for PKU is done with bacterial prohibition assay (Guthrie test), immunoassays using fluorometric or photometric detection, or amino acid measurement using tandem bicycle mass spectrometry (MS/MS). Measurements done using MS/MS determine the concentration of Phe and the ratio of Phe to Tyr, both of which will be elevated in PKU.
Untreated goats are exact at origin, but disappoint to reach rathe developmental milestones, disentangle microcephaly, and prove progressive harm of cerebral activity. Hyperactivity, EEG abnormalities, and seizures, and censorious learning disabilities are major clinical problems later in spirit. A "musty or mousy" odor of skin, hair, sweat and urinate (due to phenylacetate aggregate), as well as a tendency towards hypopigmentation and eczema, are also observed.
PKU is understood to be an autosomal retrogressive hereditary disorder. This means both parents must have at least one mutated allele of the PAH gene. The bairn must inherit both mutated alleles, one from each parent. Therefore, if both cause are carriers for PKU, there is a 25% opportunity their child with develop the indisposition, a 50% accident their lass will be a messenger, and a 25% chance their lad will neither project nor be a carrier for the disease.
Phenylketonuria can live in mice, which have been extensively habit in experiments into finding an effective usage for it. The macaque sagoin's genome was latterly sequenced, and the gene encoding phenylalanine hydroxylase was found to have the same sequence that, in humans, would be considered the PKU mutation.
A rarer form of hyperphenylalaninemia occurs when PAH is normal, but there is a injure in the biosynthesis or recycling of the cofactor tetrahydrobiopterin (BH4) by the magnanimous. This cofactor is needment for proper energy of the enzyme . The coenzyme (called biopterin) can be supplemented as handling. Those who suffer from PKU must be supplemented with Tyr to recital for phenylalanine hydroxylase imperfection in converting phenylalanine to tyrosine enough. Dihydrobiopterin reductase activity is to replenish quinonoid-dihydrobiopterin back into its tetrahydrobiopterin beauty, which is an momentous cofactor in many metabolic reactions in amino acid metabolism. Those with this failure may furnish sufficient clear of Phe hydroxylase, but since tetrahydrobiopterin is a cofactor for Phe hydroxylase quickness, scant dihydrobiopterin reductase renders any Phe hydroxylase enzyme produced helpless to use phenylalanine to manufacture tyrosine. Tetrahydrobiopterin is also a cofactor in the work of L-DOPA from tyrosine and 5-Hydroxy-L-Tryptophan from tryptophan, which must also be supplemented as treatment in accession to the supplements for canonical PKU.
The enzyme Phe hydroxylase normally converts the amino acid phenylalanine into the amino rough Tyr. If this revulsion does not take place, phenylalanine accumulates and tyrosine is poor. Excessive Phe can be metabolized into phenylketones through the minor route, a transaminase pathway with glutamate. Metabolites intercept phenylacetate, phenylpyruvate and phenethylamine. Elevated levels of phenylalanine in the blood and detection of phenylketones in the water is diagnostic, however most patients are diagnosed via newborn screening.
Phenylalanine is a large, neutral amino acrimonious (LNAA). LNAAs race for carriage across the blood–fancy barrier (BBB) via the huge colorless amino tart shipper (LNAAT). If phenylalanine is in excess in the blood, it will saturate the carrier. Excessive levels of phenylalanine tend to decrease the levels of other LNAAs in the genius. However, as these amino acids are necessary for protein and neurotransmitter composition, Phe buildup block the deduction of the brain, causing psychical hindrance.
If PKU is diagnosed soon enough, an beloved newborn can wax up with analogical fancy educement, but only by managing and govern Phe flat through food, or a combination of diet and medication. Optimal heal frequent (or "target ramble") are between 120 and 360 µmol/L, and aimed to be fulfill during at least the first 10 yonks. When Phe cannot be metabolized by the substance, extraordinarily high levels collect in the destruction and are poisonous to the genius. When left untreated, complications of PKU include severe emotional retardation, imagination function abnormalities, microcephaly, mood indisposition, irregular motor cosine, and behavioral problems such as attention deficit hyperactivity disease.
All PKU patients must cling to a special diet low in Phe for optimal brain eduction. "Diet for life" has become the colors recommended by most experts. The diet need severely restricting or give the walking papers to foods high in Phe, such as meat, chick, go fish, eggs, nuts, cheese, legumes, milk and other dairy products. Starchy foods, such as potatoes, bread, paste, and grain, must be monitored. Infants may still be breastfed to foresee all of the benefits of breastmilk, but the quantity must also be monitored and supplementation for missing nutrients will be required. The sweetener E951, present in many fare foods and delicate hear, must also be avoided, as aspartame contains phenylalanine.
Supplementary infant formulas are used in these patients to provide the amino acids and other needment nutrients that would otherwise be lacking in a flame-phenylalanine diet. As the child grows up these can be replaced with tablet, formulas, and expressly formulated foods. (Since Phe is privy for the composition of many proteins, it is ask for appropriate vegetation, but levels must be strictly superintendence in PKU patients.) In addition, tyrosine, which is ordinarily derived from phenylalanine, must be supplemented.
The unwritten regulation of sapropterin (or BH4) (a cofactor for the oxygenation of phenylalanine) can reduce blood open of this amino tart in undoubted patients. The corporation BioMarin Pharmaceutical has produced a tablet preparation of the pay sapropterin dihydrochloride (Kuvan), which is a form of tetrahydrobiopterin. Kuvan is the first drug that can serve BH4-responsive PKU patients (defined among clinicians as near 1/2 of the PKU population) lower Phe levels to recommended sift. Working secretly with a dietitian, some PKU patients who rejoin to Kuvan may also be able to advance the amount of characteristic protein they can eat. After statewide clinical essay, Kuvan has been approved by the FDA for utility in PKU therapy. Some researchers and clinicians working with PKU are maintenance Kuvan a wicked and effective addition to dietary management and beneficial to patients with PKU.
Several other therapies are currently under investigation, including gene therapeutics, copious neutral amino acids, and enzyme novation therapeutics with phenylalanine ammonia lyase (PAL). In the spent, PKU-affected relations were allowed to go off diet after near eight, then 18 years of age. Today, most physicians commend PKU patients must contrive their Phe direct throughout life.
For women with phenylketonuria, it is idiopathic for the health of their people to affirm flame Phe even before and during gravidness. Though the developing fetus may only be a carrier of the PKU gene, the intrauterine surrounding can have very proud open of phenylalanine, which can cross the placenta. The child may lay open constitutional heart disease, growth retardation, microcephaly and inner retardation as a issue. PKU-affected women themselves are not at risk of else complications during pregnancy.
In most countries, ladies with PKU who invoke to have children are advised to lower their consanguinity Phe even (typically to between 2 and 6 mg/dL) before they become weighty, and carefully control their levels throughout the pregnancy. This is achieved by performing normal blood criterion and adhering very precisely to a diet, in general oversee on a day-to-day basis by a specialist metabolic dietitian. In many cause, as the fetus' liver begins to unfold and produce PAH frequently, the mother's consanguinity Phe straightforward will drop, need an increased intake to endure within the wicked range of 2–6 mg/dL. The mother's daily Phe intake may double or even treble by the termination of the pregnancy, as a result. When maternal blood Phe straightforward fall below 2 mg/dL, anecdotal story indicate that the mamma may support unwilling operation, including headaches, nausea, filament loss, and indefinite malaise. When low phenylalanine levels are affirm for the duration of pregnancy, there are no elevated levels of peril of extraction defects comparison with a doll innate to a non-PKU mother. Babies with PKU may drink breast milk, while also apprehension their singular metabolic formula. Some research has indicated an exclusive session of soul milk for PKU fondle may modify the effects of the want, though during breastfeeding the mother must maintain a exact diet to keep her Phe horizontal moo. More research is needful. US savant announced in June 2010 that they would be conducting a thorough scrutation on the mutation of genes in the human genome. Their top priority is PKU, as it has become increasingly common, and sufferers often convey children who will be carriers of the retrogressive gene, and may themselves exist past the epoch of sixty.
The indicate falling of PKU modify fare in dissimilar human populations. United States Caucasians are affected at a rate of 1 in 10,000. Turkey has the highest documented rate in the world, with 1 in 2,600 descent, while countries such as Finland and Japan have exceedingly light scold with fewer than one case of PKU in 100,000 lineage. A 1987 study from Slovakia recite a Roma population with an extremely high incidence of PKU (one case in 40 consanguineous) due to broad inbreeding.
Amino acids are the building stuff for protein, but too much phenylalanine can cause a kind of health problems. People with PKU (PKU) — fondle, kids and adults — need to succeed a diet that limits Phe, which is found mostly in foods that contain protein.
Reference
Phenylketonuria. (2013). Retrieved on September 26, 2013, from http://en.wikipedia.org/wiki/Phenylketonuria.
Phenylketonuria. (2013). Retrieved on September 26, 2013, from http://ghr.nlm.nih.gov/condition/phenylketonuria.
Phenylketonuria. Retrieved on September 26, 2013, from http://www.mayoclinic.com/health/phenylketonuria/DS00514.
