<prompt> Pyrimidine metabolism features are all exceptRequire CAD polypeptide chain6-azauridine leads to oritidinuriaDHOA-dehydrogenase is mitochondrialIn Reye syndrome, there is decreased cytosolic carbamoyl phosphate  <response>: In Reye syndrome, cytosolic carbamoyl phosphate is increased as severely damaged mitochondria cannot utilize carbamoyl phosphate. Therefore, carbamoyl phosphate is diverted to the cytosol.It uses 2 multifunctional-multicatalytic polypeptides, which ensures efficient channeling of carbamoyl phosphate to pyrimidine synthesis.First 3 enzymes i.e. CPS II, Aspartate transcarbamoylase and Dihydroorotase are three different catalytic domain of single CAD polypeptide chain a name derived from the 1st letter of each domain.Next 4th non multifunctional enzyme DHOA dehydrogenase is the only mitochondrial enzyme.Orotate phosphoribosyltransferase and Orotidylate OMP decarboxylase are also catalytic domains of a single polypeptide chain of bifunctional enzyme UMP synthase. Orotic aciduria is caused by a defect of a single type II or both type I domains and results in poor growth, megaloblastic anemia and excretion of large amounts of orotate in urine. Uridine administration improves the condition.6-Azauridine, following conversion to 6-azauridylate, competitively inhibits orotidylate decarboxylate and therefore causes orotic aciduria and orotidinuria. 