Urea Cycle Enzymes in the Developing Human Fetus

Abstract
Carbamylphosphate synthetase, argininosuccinate cleavage enzyme, arginase and ornithine-carbamyl transferase (OCT) were determined in livers of human fetuses of different stages of development. Activity can be measured for all enzymes from the 50th day of gestation. For all enzymes, except OCT 1 or 2 peaks of concentration are observed during the 60th and 90th day of gestation. This is in connection with the fast growth rate during this period. Except arginase all reach adult values in the course of fetal development.