Oxidoreductases;
Acting on paired donors, with incorporation or reduction of molecular oxygen;
With reduced pteridine as one donor, and incorporation of one atom of oxygen into the other donor
BRITE hierarchy

L-phenylalanine,tetrahydropteridine:oxygen oxidoreductase (4-hydroxylating)

L-phenylalanine + a 5,6,7,8-tetrahydropteridine + O2 = L-tyrosine + a 4a-hydroxy-5,6,7,8-tetrahydropteridine [RN:R12540]

R12540;
(other) R01795 R07211
Reaction

L-phenylalanine [CPD:C00079];
5,6,7,8-tetrahydropteridine [CPD:C05650];
O2 [CPD:C00007]

The active centre contains mononuclear iron(II). The reaction involves an arene oxide that rearranges to give the phenolic hydroxy group. This results in the hydrogen at C-4 migrating to C-3 and in part being retained. This process is known as the NIH-shift. The 4a-hydroxytetrahydropteridine formed can dehydrate to 6,7-dihydropteridine, both spontaneously and by the action of EC 4.2.1.96, 4a-hydroxytetrahydrobiopterin dehydratase. The 6,7-dihydropteridine must be enzymically reduced back to tetrahydropteridine, by EC 1.5.1.34, 6,7-dihydropteridine reductase, before it slowly rearranges into the more stable but inactive compound 7,8-dihydropteridine.

EC 1.14.16.1 created 1961 as EC 1.99.1.2, transferred 1965 to EC 1.14.3.1, transferred 1972 to EC 1.14.16.1, modified 2002, modified 2003, modified 2019