The enzyme 4a-hydroxytetrahydrobiopterin dehydratase () catalyzes the chemical reaction
This enzyme belongs to the family of lyases, specifically the hydro-lyases, which cleave carbon-oxygen bonds. The systematic name of this enzyme class is 4a-hydroxytetrahydrobiopterin hydro-lyase (6,7-dihydrobiopterin-forming). Other names in common use include 4a-hydroxy-tetrahydropterin dehydratase, pterin-4ñ-carbinolamine dehydratase, and 4a-hydroxytetrahydrobiopterin hydro-lyase.
As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes , , and .