Catalyzes the epimerization of various hydrophobic dipeptides, such as L-Ala-L-Phe. Has epimerase activity with L-Ala-L-Thr, L-Ala-L-Met, L-Ala-L-Tyr, as well as L-Phe-L-Met, L-Phe-L-Ser and L-Phe-L-Thr (in vitro). Binds 1 Mg(2+) ion per subunit. Part of a large, functionally divergent protein family. Protein modeling and substrate docking was used to predict the substrate specificity, prior to biochemical analysis. Belongs to the mandelate racemase/muconate lactonizing enzyme family.