Allantoin: A urea hydantoin that is found in URINE and PLANTS and is used in dermatological preparations.Urate Oxidase: An enzyme that catalyzes the conversion of urate and unidentified products. It is a copper protein. The initial products decompose to form allantoin. EC 1.7.3.3.Hydantoins: Compounds based on imidazolidine dione. Some derivatives are ANTICONVULSANTS.UreohydrolasesTartronatesOxamic Acid: Amino-substituted glyoxylic acid derivative.Imidazolines: Compounds based on reduced IMIDAZOLES containing a single double bond.GlyoxylatesUrea: A compound formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end product of protein catabolism and constitutes about one half of the total urinary solids.Racemases and Epimerases: Enzymes that catalyze inversion of the configuration around an asymmetric carbon in a substrate having one (racemase) or more (epimerase) center(s) of asymmetry. (Dorland, 28th ed) EC 5.1.AmidohydrolasesUric Acid: An oxidation product, via XANTHINE OXIDASE, of oxypurines such as XANTHINE and HYPOXANTHINE. It is the final oxidation product of purine catabolism in humans and primates, whereas in most other mammals URATE OXIDASE further oxidizes it to ALLANTOIN.Guanine Deaminase: An enzyme that catalyzes the deamination of guanine to form xanthine. EC 3.5.4.3.Nitrogen Compounds: Inorganic compounds that contain nitrogen as an integral part of the molecule.Membrane Transport Modulators: Agents that affect ION PUMPS; ION CHANNELS; ABC TRANSPORTERS; and other MEMBRANE TRANSPORT PROTEINS.Amidine-Lyases: These enzymes catalyze the elimination of ammonia from amidines with the formation of a double bond. EC 4.3.2.Nitrogen: An element with the atomic symbol N, atomic number 7, and atomic weight [14.00643; 14.00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth's atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells.