Involved in the catabolism of purine nucleotides. Can use (S)-2-ureidoglycine as substrate, but not allantoate. The sequential activity of AAH, UGLYAH and UAH allows a complete purine breakdown without the intermediate generation of urea. (S)-2-ureidoglycine + H2O = (S)-ureidoglycolate + NH4(+) kcat is 761 sec(-1) for (S)-2-ureidoglycine. Homooctamer. Belongs to the UGHY family.