The cyclic-imide-hydrolyzing activity of a prokaryotic cyclic-ureide-hydrolyzing enzyme, D-hydantoinase, was investigated. The enzyme hydrolyzed cyclic imides with bulky substituents such as 2-methylsuccinimide, 2-phenylsuccinimide, phthalimide, and 3,4-pyridine dicarboximide to the corresponding half-amides. However, simple cyclic imides without substituents, which are substrates of imidase (i...