Definition of "tetrahydrobiopterin" [tetrahydrobiopterin]

• 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. (noun)

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• "Dudley and his colleagues knew that-in blood vessels-the problem was depletion of a chemical called tetrahydrobiopterin, or BH4, which is needed for the tissues to make NO."
• "Dudley and his colleagues knew that -- in blood vessels -- the problem was depletion of a chemical called tetrahydrobiopterin, or BH4, which is needed for the tissues to make NO."
• "-- the problem was depletion of a chemical called tetrahydrobiopterin, or BH4, which is needed for the tissues to make NO."