Docking studies.

aDocking studies were performed with AutoDock (version 4.2) [38] to predict the binding energy (ΔGb) of the substrate in the active site.bThe side chain of the arginine at position HB2+1 was kept fixed in the same position/rotamer as that observed for the corresponding arginine in the crystallographic structure 1BUG,A of IbCO (i.e., no flexibility was assigned to this residue during docking).cFor a second set of docking studies side chain flexibility for the arginine at position HB2+1 was allowed. The isoleucine at the corresponding position in group 1 PPOs was not given flexibility.