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Amino acid metabolism
Nitrogen and urea cycle
Citric acid cycle
Electron transport chain and oxidative phosphorylation
Pentose phosphate pathway
Physiological changes during exercise
Fatty acid oxidation
Fatty acid synthesis
Ketone body metabolism
Maple syrup urine disease
Ornithine transcarbamylase deficiency
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Hereditary fructose intolerance
Pyruvate dehydrogenase deficiency
Glycogen storage disease type I
Glycogen storage disease type II (NORD)
Glycogen storage disease type III
Glycogen storage disease type IV
Glycogen storage disease type V
Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)
Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)
Fabry disease (NORD)
Gaucher disease (NORD)
Metachromatic leukodystrophy (NORD)
Niemann-Pick disease type C
Niemann-Pick disease types A and B (NORD)
Tay-Sachs disease (NORD)
Disorders of amino acid metabolism: Pathology review
Disorders of carbohydrate metabolism: Pathology review
Disorders of fatty acid metabolism: Pathology review
Dyslipidemias: Pathology review
Glycogen storage disorders: Pathology review
Lysosomal storage disorders: Pathology review
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My PKU Life (4 Minute Version)
phenylketonuria p. 81
maternal phenylketonuria p. 82
phenylketonuria p. 82
maternal phenylketonuria p. 81
Phenylketonuria or PKU is a rare metabolic disease that can lead to severe brain disorders caused by the accumulation of the amino acid phenylalanine to toxic levels in the blood and brain.
Amino acids are the basic building blocks that make up proteins. Phenylalanine, or Phe, is one of the essential amino acids. It is necessary for life, but our bodies can't make it; therefore, Phe must be acquired through foods that contain protein. Normally, once Phe enters the body, most of it is converted to tyrosine by the enzyme phenylalanine hydroxylase. Tyrosine is then turned into neurotransmitters important for normal brain development and function.
PKU is an autosomal recessive genetic disorder that affects function of the phenylalanine hydroxylase enzyme. The phenylalanine hydroxylase gene is located on chromosome 12 and over 600 mutations have been described. The degree of enzyme function can vary. When untreated, people with PKU develop symptoms such as severe intellectual disability, psychiatric disorders, and seizures. A pregnant woman with PKU must pay special attention to her Phe levels to reduce the risk of Maternal PKU Syndrome that can result in heart defects, microcephaly, and developmental disability in her baby.
In PKU, elevated Phe levels and reduced tyrosine levels can change the way the brain functions. This is because Phe uses the same transporters to get across the blood-brain barrier as other amino acids including- tyrosine and tryptophan. Tyrosine is needed to synthesize dopamine and norepinephrine, and tryptophan is needed to synthesize the neurotransmitter serotonin. As Phe levels rise, it occupies all the transporters, making it hard for tyrosine and tryptophan to get across the blood-brain barrier. As a result, dopamine, norepinephrine, and serotonin levels in the brain begin to fall, leading to abnormal brain development and intellectual disability.
Phenylketonuria (PKU) is an autosomal recessive amino acid metabolism disorder involving impaired metabolism of the amino acid phenylalanine, caused by the absence or reduced activity of phenylalanine hydroxylase. In PKU toxic levels of phenylalanine and phenylketone build up in the body and tyrosine levels drop.
Symptoms include a musty odor of sweat and urine, intellectual disability, seizures, behavioral problems, and other neurological symptoms. In pregnant females, PKU can affect the fetus - causing heart disease, growth problems, intellectual disability, and microcephaly. Treatment is based on a diet with low levels of phenylalanine and supplementing with tyrosine and tetrahydrobiopterin.
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