The active centre contains mononuclear iron(II). The enzyme is activated by phosphorylation, catalysed by a Ca2+-activated protein kinase. The 4a-hydroxytetrahydropteridine formed can dehydrate to 6,7-dihydropteridine, both spontaneously and by the action of EC 220.127.116.11, 4a-hydroxytetrahydrobiopterin dehydratase. The 6,7-dihydropteridine must be enzymically reduced back to tetrahydropteridine, by EC 18.104.22.168, 6,7-dihydropteridine reductase, before it slowly rearranges into the more stable but inactive compound 7,8-dihydropteridine.
EC 22.214.171.124 created 1972, modified 2003, modified 2019