Description_x000D_ General description_x000D_ Tetrahydrobiopterin is a natural cofactor for phenylalanine hydroxylase, tyrosine hydroxylase, tryptophan hydroxylase, nitric oxide synthase and alkylglycerol monooxygenase._x000D_ Application_x000D_ (6R)-BH4 has been used as a buffer component for assaying tyrosine hydroxylase enzyme activity in mouse brain tissues. (6R)-BH4 has also been identified as an activator compound from a LOPAC library screen using a fluorogenic α-glucosidase assay._x000D_ Packaging_x000D_ 5, 25, 100 mg in glass bottle_x000D_ Biochem/physiol Actions_x000D_ Lack of tetrahydrobiopterin may cause hyperphenylalaninemia. Diseases like, Parkinson′s, autism, depression and Alzheimer′s shows low concentration of tetrahydrobiopterin in the cerebrospinal fluid. This coenzyme participates in dopamine (DA) synthesis._x000D_ Features and Benefits_x000D_ This compound is also offered as part of Sigma′s Library of Pharmacologically Active Compounds (LOPAC®1280), a biologically annotated collection of high-quality, ready-to-screen compounds. Click here to learn more._x000D_ This compound is featured on the Dopamine, Norepinephrine and Epinephrine Synthesis and Nitric Oxide Synthases pages of the Handbook of Receptor Classification and Signal Transduction. To browse other handbook pages, click here._x000D_ Preparation Note_x000D_ (6R)-5,6,7,8-Tetrahydrobiopterin dihydrochloride ((6R)-BH4 ) is soluble in oxygen free water at 19.60 - 20.40 mg/ml and yields a clear to slightly hazy, colorless to faint yellow solution._x000D_ Legal Information_x000D_ LOPAC is a registered trademark of Sigma-Aldrich Co. LLC