Mechanism of uricase action.
Uricase (urate:oxygen oxidoreductase, EC 1.7.3.3) exposes a positional and steric specificity in the enzymic conversion of urate to allantoin. C-2 of urate was recovered as C-2 of allantoin. By the consecutive oxidation and hydrolysis reactions a levorotatory intermediate was formed, presumably (-)-2-oxo-4-hydroxy-4-carbohydroxy-5-ureido-imidazoline. The absorption and optical rotation dispersion spectra of the intermediate were established. In the presence of borate buffer, the intermediate was transformed to (+)-alloxanate. The decay of the former compound depends on general base and acid catalysis. RS-(+/-)-allantoin was formed by chemical decarboxylation and S-(+)-allantoin by enzymic decarboxylation.
D000481:Allantoin / Q000378:metabolism; D001407:Bacillus / Q000201:enzymology; D002021:Buffers; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009905:Optical Rotatory Dispersion; D009994:Osmolar Concentration; D013053:Spectrophotometry; D013237:Stereoisomerism; D014503:Urate Oxidase / Q000378:metabolism*; D014527:Uric Acid / Q000378:metabolism
D002021:Buffers; D014527:Uric Acid; D000481:Allantoin; D014503:Urate Oxidase