... cofactor for tyrosinehydroxylase (TH) and tryptophan hydroxylase (TPH),both of which are involved in dopamine and serotoninbiosynthesis (Figure 4). Alcohol is known to interactwith the dopamine ... anintermediate, 6-pyruvoyl-tetrahydropterin (PPH4), to 1’-OXPH4, or 2’-OXPH4, and catalyzes the final step of tetrahydrobiopterin (BH4) synthesis, anessential cofactor for phenylalanine hydroxylase, ... hydroxylase, tyrosine hydroxylase (TH), tryptophan hydroxylase (TPH) and nitric oxide synthase (NOS) [65,66].Quinoid dihydropteridine reductase (QDPR) mediates reduction of quinonoid dihydrobiopterin....