This product ships with Ice Packs and it is not returnable or refundable.
*** THIS PRODUCT SHIPS WITH AN ICE PACK HOWEVER IT WILL ARRIVE WITH THE ICE-PACK MELTED AND THE PTERIDIN-4 WILL BE AT REGULAR ROOM TEMP OR A BIT WARMER DEPENDING ON YOUR LOCATION.
PLEASE NOTE THAT IF YOU SELECT OUR FREE SHIPPING OPTION, YOUR ORDER WILL ARRIVE BY REGULAR MAIL OR GROUND WHICH MAY TAKE UP TO A WEEK IN SOME CASES. IF YOU ARE CONCERNED ABOUT LONG DELIVERY FOR THIS PRODUCT WE RECOMMEND YOU SELECT ANY OF THE FEDEX EXPRESS SHIPPING OPTIONS AT CHECKOUT.
Tetrahydrobiopterin was discovered to play a role as an enzymatic cofactor. The first enzyme found to use tetrahydrobiopterin is phenylalanine hydroxylase (PAH).
Tetrahydrobiopterin is biosynthesized from guanosine triphosphate (GTP) by three chemical reactions mediated by the enzymes GTP cyclohydrolase I (GTPCH), 6-pyruvoyltetrahydropterin synthase (PTPS), and sepiapterin reductase (SR).
Tetrahydrobiopterin has the following responsibilities as a cofactor:
- Tryptophan hydroxylase (TPH) for the conversion of L-tryptophan (TRP) to 5-hydroxytryptophan (5-HTP)
- Phenylalanine hydroxylase (PAH) for conversion of L-phenylalanine (PHE) to L-tyrosine (TYR)
- Tyrosine hydroxylase (TH) for the conversion of L-tyrosine to L-DOPA (DOPA)
- Nitric oxide synthase (NOS) for conversion of a guanidino nitrogen of L-arginine (L-Arg) to nitric oxide (NO)
- Alkylglycerol monooxygenase (AGMO) for the conversion of 1-alkyl-sn-glycerol to 1-hydroxyalkyl-sn-glycerol
This supplement can be taken with or without food, morning or evening.