With EpmA is involved in the beta-lysylation step of the post-translational modification of translation elongation factor P (EF-P) on 'Lys-34'. EpmB appears to act before EpmA. Displays lysine 2,3-aminomutase activity, producing (R)-beta-lysine from (S)-alpha-lysine (L-lysine). Cannot use (S)-ornithine or (R)-alpha-lysine as a substrate