Enzymatic cofactors for the two reactions necessary for serotonin synthesis are tetrahydrobiopterin (BH4) and pyridoxine (vitamin B6), respectively. Tryptophan hydroxylase is dependent on the cofactor tetrahydrobiopterin, the recycling of which relies on folic acid (vitamin B9) metabolism.

Tetrahydrobipterin (BH4) is a pivotal enzymatic cofactor required for the synthesis of serotonin, dopamine and nitric oxide. BH4 is essential for numerous physiological processes at periphery and central levels, such as vascularization, inflammation, glucose homeostasis, regulation of oxidative stress and neurotransmission.

Degradation of serotonin is via monoamine oxidase type A and aldehyde dehydrogenase to the major serotonin metabolite 5-hydroxyindoleacetic acid (5HIAA). Levels of serotonin are also influenced by the tryptophan-degrading enzyme, indoleamine 2,3-dioxygenase and tetrahydrobiopterin, the cofactor of tryptophan hydroxylase.

Tetrahydrobipterin (BH4) is a pivotal enzymatic cofactor required for the synthesis of serotonin, dopamine and nitric oxide. BH4 is essential for numerous physiological processes at periphery and central levels, such as vascularization, inflammation, glucose homeostasis, regulation of oxidative stre …

The enzyme requires both molecular oxygen and a reduced pteridine cofactor, such as l-erythro-tetrahydrobiopterin (BH 4), for activity. In the enzymatic reaction, one atom of oxygen is used to form 5-HTP and the other is reduced to water.