Catalyzes the catabolism of the allantoin degradation intermediate (S)-ureidoglycolate, generating urea and glyoxylate. Involved in the anaerobic utilization of allantoin as sole nitrogen source. Reinforces the induction of genes involved in the degradation of allantoin and glyoxylate by producing glyoxylate. (S)-ureidoglycolate = glyoxylate + urea Nitrogen metabolism; (S)-allantoin degradation. Homodimer. Belongs to the ureidoglycolate lyase family.