This enzyme is necessary to metabolize phenylalanine to tyrosine. When the activity of the enzyme is reduced, phenylalanine accumulates and is converted to phenylketones, including phenylacetate, phenylpyruvate, and phenyllactate, that accumulate in the blood and urine.
Phenylalanine hydroxylase requires tetrahydrobiopterin as a cofactor and decreased tetrahydrobiopterin can cause decreased activity of phenylalanine hydroxylase.
This disease is inherited in an autosomal recessive fashion.
Because tyrosine can no longer be synthesized, it becomes an essential amino acid.
If diagnosed early enough, a newborn can grow with normal brain development by decreasing phenylalanine in the diet. Phenylalanine is contained in aspartame containing products like NutraSweet.
Phenylketones contain an aromatic amino group, which causes a musty or mousy body odor in individuals, which is characteristic for phenylketonuria.
Infants with phenylketonuria fail to grow at an appropriate rate and also fail to attain early developmental milestones.
Seizures are transient episodes of abnormal excessive neuronal activity in the brain. Seizures can be seen in individuals with phenylketonuria.
Infants with untreated phenylketonuria can display severely impaired cognitive functioning with deficits in two or more adaptive behaviors.
Hypopigmentation, or loss of pigmentation in the skin, is commonly observed in individuals with phenylketonuria due to decrease in the amino acid tyrosine, which is used by melanocytes to make melanin.
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