Involved in tetrahydrobiopterin biosynthesis. Seems to both prevent the formation of 7-pterins and accelerate the formation of quinonoid-BH2. Coactivator for HNF1A-dependent transcription. Regulates the dimerization of homeodomain protein HNF1A and enhances its transcriptional activity.
Defects in PCBD1 are the cause of BH4-deficient hyperphenylalaninemia type D (HPABH4D) [MIM:264070]; also known as hyperphenylalaninemia with primapterinuria. HPABH4D is characterized by the excretion of 7-substituted pterins in the urine of affected patients.
Belongs to the pterin-4-alpha-carbinolamine dehydratase family.