Binding to a tetrahydrobiopterin, 5,6,7,8-tetrahydrobiopterin or a derivative thereof; tetrahydrobiopterins are enzyme cofactors that carry electrons in redox reactions.
Reactome:R-HSA-1497784 "The cofactor BH4 is required for electron transfer in the eNOS catalytic cycle"
;
Reactome:R-HSA-1497796 "BH2 binding can lead to eNOS uncoupling"