IUBMB Enzyme Nomenclature


Accepted name: phenylalanine 3-monooxygenase

Reaction: L-phenylalanine + a 5,6,7,8-tetrahydropteridine + O2 = 3-hydroxy-L-phenylalanine + a 4a-hydroxy-5,6,7,8-tetrahydropteridine

Glossary: 3-hydroxy-L-phenylalanine = meta-L-tyrosine = 3-(3-hydroxyphenyl)-L-alanine

Other name(s): PacX; phenylalanine 3-hydroxylase

Systematic name: L-phenylalanine,tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating)

Comments: The enzyme, characterized from the bacterium Streptomyces coeruleorubidus, forms 3-hydroxy-L-phenylalanine (i.e. m-L-tyrosine), which is one of the building blocks in the biosynthesis of the uridyl peptide antibiotics pacidamycins. The 4a-hydroxytetrahydropteridine formed can dehydrate to 6,7-dihydropteridine, both spontaneously and by the action of EC, 4a-hydroxytetrahydrobiopterin dehydratase. The 6,7-dihydropteridine must be enzymically reduced back to tetrahydropteridine, by EC, 6,7-dihydropteridine reductase, before it slowly rearranges into the more stable but inactive compound 7,8-dihydropteridine.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Zhang, W., Ames, B.D. and Walsh, C.T. Identification of phenylalanine 3-hydroxylase for meta-tyrosine biosynthesis. Biochemistry 50 (2011) 5401-5403. [PMID: 21615132]

[EC created 2014, modified 2019]

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