Involved in the asymmetric conversion of racemic 5-substituted hydantoins to the corresponding L-amino acids. Catalyzes the racemization via enolization of D- and L-5-monosubstituted hydantoins. Is able to racemize 5-substituted hydantoins having either aromatic or aliphatic substituents such as D- and L-5-(2-methylthioethyl)hydantoin. a D-5-monosubstituted hydantoin = a L-5-monosubstituted hydantoin Strongly inhibited by Cu(2+) and Zn(2+). Slightly stimulated by of Mn(2+) or Co(2+), but also by metal-chelating agents such as EDTA or EGTA. Optimum pH is 9.5. Optimum temperature is 45 degrees Celsius. Homohexamer. Belongs to the HyuE racemase family.