Aspartate carbamoyltransferase activity in rat liver at different stages of its development

Aspartate carbamoyltransferase (ACTase) activity has been measured in rat livers at different stages of their development and in intact and regenerating livers. The level of enzyme activity was found to be the highest in the earliest fetal livers (about 7 times higher than in the adult rat liver). Deproteinized by heating, supernatants of sheep liver homogenates were purified on a Sephadex G-25 column. The influence of deproteinized supernatant on ACTase activity in rat liver was measured. This influence depended on the amount of activating factor added to fresh homogenates. A different scope of activation of enzyme activity in rat liver caused by deproteinized supernatant was noticed. The greatest increase of enzyme activity under the influence of activating factor was obtained in the liver of young animals, mothers and old female rats, the smallest in fetuses and very young animals. A relatively smaller increase of enzyme activity was observed in regenerating livers under the same experimental conditions. In this article the role of natural ACTase activator is discussed.