Utilization of purines as secondary nitrogen sources, when primary sources are limiting. allantoate + H2O = (S)-ureidoglycolate + urea Nitrogen metabolism; (S)-allantoin degradation; (S)-ureidoglycolate from allantoate (aminidohydrolase route): step 1/1. Abundantly expressed in kidney and liver, but at much lower level is also present in brain, testis, intestine and lung. Belongs to the allantoicase family.