Hydrolyzes most efficiently N-acetyl derivatives of aromatic amino acids but is also active on other amino acids. L-stereospecific. an N-acyl-L-amino acid + H2O = a carboxylate + an L-alpha-amino acid an N-acetyl-L-cysteine-S-conjugate + H2O = acetate + an S-substituted L-cysteine Homotetramer. Belongs to the peptidase M20 family.