Fig. 4. Mechanistic insights into the second FIH-catalysed hydroxylation of (D)-leucine.

a Potential energy profiles for the ‘second’ hydroxylation of (2R,3S) C3 hydroxyleucine (brown) and (2S,3R) C3 hydroxyleucine (blue) substrates. The potential energies of stationary-state structures on the reaction coordinates are measured from the respective reactant complexes (SDR2 and RLR2). b Optimized structures of energy minima and transition states for the ‘second’ hydroxylation reaction of the (2R,3S) C3 hydroxyleucine substrate. c Optimized structures of the energy minima and the transition state for the ‘second’ hydroxylation reaction of the (2S,3R) C3 hydroxyleucine substrate. Colours: Fe (blue purple), N (blue), O (red), C (turquoise), substrate (D)-leucine (yellow-green), (L)-leucine (orange), H (white). Selected distances are in Å.