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Tetrahydrobiopterin deficiency (THBD, BH 4 D) is a rare metabolic disorder that increases the blood levels of phenylalanine.Phenylalanine is an amino acid obtained normally through the diet, but can be harmful if excess levels build up, causing intellectual disability and other serious health problems.
Phenylketonuria (PKU)-like symptoms, including more pronounced developmental defects, skin irritation, and vomiting, may appear when phenylalanine levels are near 20 mg/dL (1200 mol/L). [1] Hyperphenylalaninemia is a recessive hereditary metabolic disorder that is caused by the body's failure to convert phenylalanine to tyrosine as a result of ...
It is a 4-hydroxyphenylpyruvate dioxygenase inhibitor indicated for the treatment of hereditary tyrosinemia type 1 (HT-1) in combination with dietary restriction of tyrosine and phenylalanine. [7] Liver transplant is indicated for patients with tyrosinemia type I who do not respond to nitisinone, as well as those with acute liver failure and ...
Patients received amino acid supplements lacking tyrosine and phenylalanine, most often by drinking a specially engineered formula, in order to acquire sufficient protein. It is recommended that tyrosine levels remain below 500 μmol/L. [5] Phenylalnine is the precursor to tyrosine. The ideology behind maintaining low tyrosine levels is two-fold.
Phenylalanine is a large, neutral amino acid (LNAA). LNAAs compete for transport across the blood–brain barrier (BBB) via the large neutral amino acid transporter (LNAAT). If phenylalanine is in excess in the blood, it will saturate the transporter. Excessive phenylalanine levels tend to decrease the levels of other LNAAs in the brain.
Inborn errors of metabolism are often referred to as congenital metabolic diseases or inherited metabolic disorders. [2] Another term used to describe these disorders is "enzymopathies". This term was created following the study of biodynamic enzymology , a science based on the study of the enzymes and their products.
The absence of BH 4 affects the metabolism of Phenylalanine. This is the reason that PKU and PTPS deficiency share some similar symptoms. However, since BH 4 is needed for much more than just the metabolism of Phenylalanine, there are other symptoms as well. [7]
In those with dopamine-responsive dystonia, symptoms typically dramatically improve with low-dose administration of levodopa, which is a biochemically significant metabolite of the amino acid phenylalanine, as well as a biological precursor of the catecholamine dopamine, a neurotransmitter. (Neurotransmitters are naturally produced molecules ...