EC - 4a-hydroxytetrahydrobiopterin dehydratase

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IntEnz Enzyme Nomenclature


Accepted name:
4a-hydroxytetrahydrobiopterin dehydratase
Other names:
4α-hydroxy-tetrahydropterin dehydratase
pterin-4α-carbinolamine dehydratase
tetrahydrobiopterin dehydratase
4a-hydroxytetrahydrobiopterin hydro-lyase
Systematic name:
(6R)-6-(L-erythro-1,2-dihydroxypropyl)-5,6,7,8-tetrahydro-4a-hydroxypterin hydro-lyase [(6R)-6-(L-erythro-1,2-dihydroxypropyl)-7,8-dihydro-6H-pterin-forming]



In concert with EC, 6,7-dihydropteridine reductase, the enzyme recycles 4a-hydroxytetrahydrobiopterin back to tetrahydrobiopterin, a cosubstrate for several enzymes, including aromatic amino acid hydroxylases. The enzyme is bifunctional, and also acts as a dimerization cofactor of hepatocyte nuclear factor-1α (HNF-1).

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0008124
UniProtKB/Swiss-Prot: (258) [show] [UniProt]


  1. Citron, B. A., Davis, M. D., Milstien, S., Gutierrez, J., Mendel, D. B., Crabtree, G. R., Kaufman, S.
    Identity of 4a-carbinolamine dehydratase, a component of the phenylalanine hydroxylation system, and DCoH, a transregulator of homeodomain proteins.
    Proc. Natl. Acad. Sci. U.S.A. 89 : 11891-11894 (1992). [PMID: 1465414]
  2. Hauer, C.R., Rebrin, I., Thöny, B., Neuheiser, F., Curtius, H.C., Hunziker, P., Blau, N., Ghisla, S., Heizmann, C.W.
    Phenylalanine hydroxylase-stimulating protein/pterin-4α-carbinolamine dehydratase from rat and human liver. Purification, characterization, and complete amino acid sequence.
    J. Biol. Chem. 268 : 4828-4831 (1993). [PMID: 8444860]
  3. Thony, B., Neuheiser, F., Blau, N., Heizmann, C. W.
    Characterization of the human PCBD gene encoding the bifunctional protein pterin-4 alpha-carbinolamine dehydratase/dimerization cofactor for the transcription factor HNF-1 alpha.
    Biochem. Biophys. Res. Commun. 210 : 966-973 (1995). [PMID: 7763270]
  4. Endrizzi, J. A., Cronk, J. D., Wang, W., Crabtree, G. R., Alber, T.
    Crystal structure of DCoH, a bifunctional, protein-binding transcriptional coactivator.
    Science 268 : 556-559 (1995). [PMID: 7725101]
  5. Cronk, J. D., Endrizzi, J. A., Alber, T.
    High-resolution structures of the bifunctional enzyme and transcriptional coactivator DCoH and its complex with a product analogue.
    Protein Sci. 5 : 1963-1972 (1996). [PMID: 8897596]

[EC created 1999, modified 2020]