Isomerization is feasible for all the intermediates formed during the catalytic cycle (Figure ). While water and molecular oxygen in intermediates (1) and ( ) are represented in axial positions due to the frequency with which this isomer is observed in crystal structures of hydroxylases 119,122-124 , these intermediates can also have equatorial configurational isomers where water and molecular oxygen are in equatorial positions (Figure ). In Fe(IV)=O and Fe(III)-OH intermediates, the active site can have a six-coordinate tetragonal or a five-coordinate square pyramidal geometry around iron depending on whether succinate and Asp/Glu are coordinated to iron in a bidentate or monodentate configuration (Figure and Supporting Information Figure ).