Metabolism of allantoin in soybeans

The metabolism of [2-7 14C] and [4-5 14C] allantoin has been studied in intact leaf tissue to elucidate the pathway of allantoin catabolism and its regulation. 1.3 mM [2-7 14C] and 1.3 mM [4-5 14C] DL allantoin release 14CO2 from intact leaf discs at 0.9 and 0.08 μmoles.hr-1.g fresh wt-1 respectively. The most potent urease inhibitor known, phenyl phosphordiamidate (PPD), inhibited urease in intact tissue at concentrations from 0.1 mM to 10 mM. In contrast 14CO2 release from [2-7 14C] and [4-5 14C] allantoin was not inhibited by 1 mM PPD in 0.5 h and 1 h assays. These data are consistent with allantoate amido-hydrolase action. Intact tissue discs were incubated with [4-5 14C] allantoin and analyzed for catabolites by ion exclusion HPLC. Allantoate, ureidoglycolate, and glyoxylate were identified by their retention time. Two 14C labelled peaks did not migrate with known standards. They are being characterized to identify their structure. These data are consistent with a pathway of catabolism including allantoate, ureidoglycolate and glyoxylate, NH3 and CO2