excreted by Birds Reptile allantoicase Insects COOH H H Uric acid CHO Glyoxylic acid 2H2O+ urate oxidase CO +ho 2H2N一C-NH2 Cartilaginous fish rea HoN 2H.O 0 Other mammals urease N H 2C0 H H Allantoin Marine invertebrates H2O allantoinase COOH NH Teleost fish Fi The degradation of uric acid to ammonia. The process is arrested at different ONHN stages in the indicated species, and the resulting nitrogen-containing product is excreted Allantoic acid