Residue 662 is located on loop 5 between the 5 sheet and 5
helix of domain A, which is interesting for the substrate interaction
and active site reactivity [4]. Substituting of this residue by Arg may
introduce two new hydrogen bonds with Q664 and T667 (Fig. 6B).
These two additional hydrogen bonds may interfere with the ability
of loop 5 to assist in catalysis through hydrogen bonding to the
substrate, thereby affecting the catalytic efficiency of the mutant.