This pathway shows disorders related to phenylalanine and tetrahydrobiopterin (BH4) metabolism. Disorders resulting from an enzyme defect are highlighted in pink. Pathological metabolites used as specific markers are highlighted in purple. BH4 is a natural cofactor for PAH, tyrosine-3-hydroxylase, tryptophan-5-hydroxylase and nitric oxide synthase (NOS), where the latter two are key enzymes in the biosynthesis of the neurotransmitters dopamine and serotonin.
This pathway was inspired by Edition 5, Chapter 20 of the book of Blau (ISBN 9783030677268) (Ed.4 Chapter 1).