Molecular basis of enzyme abnormalities in urea cycle disorders. With special reference to citrullinemia and argininosuccinic aciduria.

This paper deals with enzymological, immunochemical and molecular genetic analyses of citrullinemia and argininosuccinic aciduria. Citrullinemia has been classified by Saheki et al. [J. inher. Metab. Dis. 8: 155-156, 1985] into three types from the properties of the deficient argininosuccinate synthetase (ASS) of the patients. Analysis of hepatic mRNA coding for ASS revealed certain characteristics in type II and III citrullinemic patients whose hepatic ASS protein was low. A newly developed enzyme-linked immunosorbent assay (ELISA) of argininosuccinate lyase (ASL) protein showed that 8 out of ten cases of argininosuccinic aciduria had no detectable ASL protein in the liver, erythrocytes, cultured skin fibroblasts or cultured amniocytes.