biochemical aspects of phenylketonuria disease
Defects in the metabolism of phenylalanine is the main reason for Phenylketonuria (PKU) which is autosomal recessive disorder. PKU is a hyperphenylalaninemia with mutlifactorial causes HPAs. There are several hyperphenylalaninemias that are not PKU and are called non-PKU hyperphenylalaninemias (HPAs).
Hyperphenylalaninemia is defined as a plasma phenylalanine concentration >120μM. PKU is characterized by plasma phenylalanine >1000μM Non-PKU hyperphenylalaninemias have plasma phenylalanine amounts that are <1000μM.
Mutation in the phenylalanine hydroxylase gene (gene symbol: PAH) leads to PKU. The HPAs are disorders of phenylalanine hydroxylation.
Hydroxylation of phenylalanine occurs by PAH enzyme. This reaction catalyzed by PAH involves tetrahydrobiopterin (BH4) as a co-factor, Here HPAs are produced from defects in any of the several genes required for synthesis and recycling of BH4. Then excess of phenylalanine removed via tyrosine biosynthesis reaction and then via tyrosine catabolism.
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