Tetrahydrobiopterin

Tetrahydrobiopterin is a cofactor in the synthesis of nitric oxide. It is also essential in the conversion of phenylalanine to tyrosine by the enzyme phenylalanine-4-hydroxylase; the conversion of tyrosine to L-dopa by the enzyme tyrosine hydroxylase; and conversion of tryptophan to 5-hydroxytryptophan via tryptophan hydroxylase.

A defect in BH₄ production and/or a defect in the enzyme dihydropteridine reductase (DHPR) causes phenylketonuria type IV, as well as dopa-responsive dystonias.

Tetrahydrobiopterin is synthesized from GTP via two intermediates.

Thony B, Auerbach G, Blau N (2000). “Tetrahydrobiopterin biosynthesis, regeneration and functions”. Biochem J. 347 Pt 1: 1–16. PMID 10727395.CS1 maint: Multiple names: authors list (link)

• Tetrahydrobiopterin deficiency This can also cause mental retardation as seen in patients with Phenylketonuria (PKU).

• coenzyme tetrahydrobiopterin (BH4)
• The Tetrahydrobiopterin website

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