[Molecular basis of urea cycle disorders].

Five different enzymes, carbamyl phosphate synthetase I (CPS I), ornithine transcarbamylase (OTC) argininosuccinate synthetase (AS), argininosuccinate lyase (AL) and arginase (AR) play a role in urea synthesis from ammonium. The structures of cDNA of all these enzymes and those of genome DNA of some enzymes (OTC, AL, AR) have been already clarified, and using of the information, the alleles of each enzyme deficiency have been identified. Alleles are extremely heterogeneous in all enzyme deficiencies, in sharp difference from other inborn errors of metabolism, such as cystic fibrosis and hemoglobinopathies.