Broad specificity dipeptide epimerase. Catalyzes the epimerization of L-Ala-L-Ala, L-Ala-L-Glu, L-Ala-L-Ser, L-Ala-L-Thr and L-Ala-L-Met (in vitro). Binds 1 Mg(2+) ion per subunit. Part of a large, functionally divergent protein family. Protein modeling and substrate docking were used to predict the substrate specificity, prior to biochemical analysis. Belongs to the mandelate racemase/muconate lactonizing enzyme family.