PCBD1 enzyme takes part in phenylalanine hydroxylation. PCBD1 deficiency results in hyperphenylalaninemia. PCBD1 enzyme controls the homodimerization of HNF1. PCBD1 takes part in tetrahydrobiopterin biosynthesis. PCBD1 prevents the formation of 7-pterins and accelerate the formation of quinonoid-BH2. PCBD1 is a coactivator for HNF1A-dependent transcription.