ID 1.14.16.1 DE phenylalanine 4-monooxygenase. AN PAH. AN phenylalaninase. AN phenylalanine 4-hydroxylase. AN phenylalanine hydroxylase. CA (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin + L-phenylalanine + O2 = CA (4aS,6R)-4a-hydroxy-L-erythro-5,6,7,8-tetrahydrobiopterin + L-tyrosine. CC -!- The reaction involves an arene oxide which rearranges to give the CC phenolic hydroxy group. CC -!- This results in the hydrogen at C-4 migrating to C-3 and in part CC being retained, a process known as the NIH-shift. CC -!- The 4a-hydroxytetrahydrobiopterin formed can dehydrate to 6,7- CC dihydrobiopterin, both spontaneously and by the action of CC EC 4.2.1.96. CC -!- The 6,7-dihydrobiopterin can be enzymically reduced back to CC tetrahydrobiopterin, by EC 1.5.1.34, or slowly rearranges into the CC more stable compound 7,8-dihydrobiopterin. CC -!- Formerly EC 1.14.3.1 and EC 1.99.1.2. DR Q2KIH7, PH4H_BOVIN ; P90925, PH4H_CAEEL ; Q9A7V7, PH4H_CAUVC ; DR A8HQD7, PH4H_CHLRE ; P30967, PH4H_CHRVO ; Q54XS1, PH4H_DICDI ; DR P17276, PH4H_DROME ; P00439, PH4H_HUMAN ; P16331, PH4H_MOUSE ; DR E5KBU4, PH4H_PHYPA ; E5KBU3, PH4H_PINTA ; P43334, PH4H_PSEAE ; DR Q8XU39, PH4H_RALN1 ; P04176, PH4H_RAT ; Q98D72, PH4H_RHILO ; DR Q9KLB8, PH4H_VIBCH ; //