Given this mechanism, the mutant LSD1 with the Lys661Ala substitution is unlikely to adversely impact the interaction of LSD1 with various substrates, but rather leads to less efficient flavin recycling, which presumably then proceeds at the whim of any available non-specifically bound substitute water around that face of the FAD binding site.
As a result of this process, the mutant LSD1 with the Lys661Ala substitution is unlikely to disrupt its interaction with various substrates, but rather results in reduced flavin recycling efficiency, which then proceeds according to the availability of non-specifically bound water molecules at that FAD binding site.