URAD (ureidoimidazoline (2-oxo-4-hydroxy-4-carboxy-5-) decarboxylase) catalyzes the stereoselective decarboxylation of 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline (OHCU) to (S)-allantoin, functioning as a carboxy-lyase enzyme in purine catabolism. In humans, URAD represents one of several purine degradation enzymes retained as protein-coding transcripts despite evolutionary loss of earlier pathway components like uricase 1. While uric acid serves as the endpoint of purine catabolism in Homo sapiens due to non-functional uricase genes, URAD transcript production suggests potential regulatory roles in purine metabolism despite apparent loss of enzymatic activity 1. Recent evidence indicates URAD localizes to peroxisomes, where it may participate in cellular antioxidant defense 2. A deleterious missense variant (rs9579139) in URAD demonstrates significant association with pancreatic ductal adenocarcinoma risk (P = 2.46 × 10⁻⁹), independent of ethnicity 2. The proposed mechanism links URAD dysfunction to impaired peroxisomal reactive oxygen species elimination, potentially exposing cells to increased DNA damage and elevated cancer risk 2. These findings suggest URAD may have relevance beyond classical purine metabolism, warranting further investigation into its role in cellular redox homeostasis and cancer pathogenesis.