Possible Interaction: Ascorbate and Tetrahydrobiopterin

“ Ascorbate also regulates nitric oxide concentration by releasing nitric oxide from adducts and by acting through tetrahydrobiopterin ( BH4 ) to stimulate endothelial nitric oxide synthase (eNOS).”

“ Ascorbate , thus, seems to regulate the NOS activity in the PMNs through tetrahydrobiopterin.”

“The augmentation of NOS activity in the PMN homogenate by tetrahydrobiopterin was significantly enhanced by ascorbate , while ascorbate alone did not influence the NOS activity.”

“Pretreatment of human umbilical vein endothelial cells with ascorbate (1 μm to 1 mm, 24 h) led to an up to 3-fold increase of intracellular tetrahydrobiopterin levels that was concentration-dependent and saturable at 100 μm.”

“Significant positive correlations between BH4 and ascorbate and between BH₂-to-BH₄ ratio and DHA were observed (P < .0001 both cases).”

“Intracellular levels of tetrahydrobiopterin (BH4), a cofactor for iNOS, were increased by ascorbate in RAW 264.7 cells.”

“BH4 has been suggested to be a target for oxidation by peroxynitrite (ONOO–), and ascorbate has been shown to preserve BH4 levels and enhance endothelial NO• production; however, the mechanisms underlying these processes remain poorly defined.”

“ l-Ascorbate stimulates the enzymic hydroxylation of phenylalanine in vitro by recycling tetrahydrobiopterin , which reduces O(2) utilized in the reaction.”