XDH and hyperuricemia: Solving this pathologic model for the hyperuricemia metabolic pathway, we find that the abnormal level of uric acid obtained by the pathologic model is 20, and 16 reactions have non-zero fluxes, including the reactions catalyzed by xanthine oxidase, phosphoribosylpy-rophosphate synthetase, hypoxanthine phosphoribosyltransferase, IMP dehydrogenase, AMP deaminase, adenine deaminase, 5’-nucleotidase, etc. The reaction synthesizing PRPP has the highest flux, which is consistent with the fact that functional defect in the enzyme phosphoribosylpy-rophosphate (PRPP) synthetase causes hyperuricemia.