As nouns the difference between tetrahydrobiopterin and biopterin

is that tetrahydrobiopterin is (biochemistry) a naturally-occurring nutrient and essential cofactor of the three aromatic amino acid hydroxylase enzymes, used in the biosynthesis of the neurotransmitters serotonin, melatonin, dopamine, norepinephrine, epinephrine, and nitric oxide while biopterin is a coenzyme produced within the body, an oxidized degradation product of tetrahydrobiopterin defects in biopterin synthesis or regeneration can cause a form of hyperphenylalaninemia, and biopterin deficiency has been associated with dystonia and rabies.