Abstract
Hyperammonemia is observed regulary in patients with Reye's Syndrome /RS/, and may be a crucial determinant of the encephalopathy in this often lethal condition. Since ammonia detoxification depends on an intact urea cycle and since patients with inherited defects of a single urea cycle enzyme also demonstrate hyperammonemia, we sought to define the mechanism of hyperammonemia in RS by examining activities of the first two urea cycle enzymes, carbamyl phosphate synthetase I /CPS I/ and ornithine transcarbamylase /OTC/ in liver homogenates from 4 RS patients. OTC activity was reduced to 10–15 % of control mean in 2 autopsy specimens and to 40–42 % of control in 2 biopsy samples. In 2 livers Km's for the substrates, ornithine /Orn/ and carbamyl phosphate /Cp/, were normal and the Vmax's were much reduced; in a third, the Km's for Orn and Cp were increased 10 fold and 5 fold, respectively, but the Vmax's were normal. Significantly CPS I activity was normal in all 4 livers and activity of a third urea cycle enzyme, arginase, was normal in the one RS liver assayed. These data suggest that specific deficiency of OTC activity may be responsible for the hyperammonemia in RS and that more then one kind of kinetic disturbance may underlie the OTC impairment.
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Francois, B., Ricciuti, F. & Rosenberg, L. ORNITHINE TRANSCARBAMYLASE DEFICIENCY IN REYE'S SYNDROME. Pediatr Res 9, 863 (1975). https://doi.org/10.1203/00006450-197511000-00070
Issue Date:
DOI: https://doi.org/10.1203/00006450-197511000-00070