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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.
Tyrosine is semi-essential; therefore, it can be synthesized by the animal, but only from phenylalanine. Phenylketonuria, a genetic disorder that occurs as a result of the inability to breakdown phenylalanine, is due to a lack of the enzyme phenylalanine hydroxylase. A dietary lack of tryptophan can cause stunted skeletal development. [9]
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 levels of phenylalanine tend to decrease the levels of other LNAAs in the brain.
It is a rare disease in dogs, with cats seven to ten times more likely to be infected. The disease in dogs can affect the lungs and skin, but more commonly the eye and central nervous system. [20] Ringworm is a fungal skin disease that in dogs is caused by Microsporum canis (70%), Microsporum gypseum (20%), and Trichophyton mentagrophytes (10% ...
Phenylalanine is a precursor for tyrosine, the monoamine neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), and the biological pigment melanin. It is encoded by the messenger RNA codons UUU and UUC. Phenylalanine is found naturally in the milk of mammals.
Hawkinsinuria is an autosomal dominant metabolic disorder affecting the metabolism of tyrosine. [1] [2] Normally, the breakdown of the amino acid tyrosine involves the conversion of 4-hydroxyphenylpyruvate to homogentisate by 4-hydroxyphenylpyruvate dioxygenase. Complete deficiency of this enzyme would lead to tyrosinemia III. In rare cases ...
Phe—phenylalanine, Tyr—tyrosine, pHPP—p-hydroxyphenylpyruvate, hga—homogentisate, maa—maleylacetoacetate, faa—fumarylacetoacetate. Enzymes: PAH—phenylalanine hydroxylase, TAT—tyrosine transaminase, HPD—4-hydroxyphenylpyruvate dioxygenase, HGD—homogentisate oxidase, MAAI—maleylacetoacetate isomerase, FAH—fumarylacetoacetase.
Hyperphenylalaninemia is a recessive hereditary metabolic disorder that is caused by the body's failure to convert phenylalanine to tyrosine as a result of the entire or partial absence of the enzyme phenylalanine hydroxylase. [3]