Catalyzes the epimerization of L-Ala-D-Glu to L-Ala-L-Glu and has probably a role in the metabolism of the murein peptide, of which L-Ala-D-Glu is a component. Is also able to catalyze the reverse reaction and the epimerization of the other Ala-X dipeptides L-Ala-L-Asp, L-Ala-L-Leu, L-Ala-L-Met, and L-Ala-L-Ser. Is not able to epimerize other L-Ala-X dipeptides. Is also active with L-Ser-L-Glu and, oddly, L-Pro-L-Glu, but not with L-Glu-L-Glu, L-Lys-L-Glu, L-Lys-L-Ala, or D-Ala-D-Ala. L-alanyl-L-glutamate = L-alanyl-D-glutamate Binds 1 Mg(2+) ion per subunit. The catalytic efficiency is 25-fold higher with L-Ala-D-Glu than with L-Ala-D-Asp or L-Ala-D-Met as substrate. Cell wall degradation; peptidoglycan degradation. Homooctamer; tetramer of dimers. Repressed by AbrB, a transcription factor that negatively controls biofilm formation. Belongs to the mandelate racemase/muconate lactonizing enzyme family.