Has epimerase activity with a variety of hydrophobic dipeptides (in vitro). Enzyme activity is highest with L-Phe-L-Tyr, but is still relatively low, suggesting that L-Phe-L-Tyr is not the physiological substrate. Binds 1 Mg(2+) ion per subunit. kcat is 4.7 sec(-1) for epimerization of L-Phe-L-Tyr. 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.