Changes in tyrosine transaminase and phosphoenolpyruvate kinase activities during short term incubation of fetal liver.

Incubation of fetal rat liver homogenates at 37 degrees for 2-3 hr increased PEPK activity in the 100,000 X g supernatant 5-fold and TTA activity 10-fold. At the same time, activity in the 100,000 X g pellet decreaed and no change was observed in the whole homogenate. It is concluded that during incubation of fetal liver pieces or homogenates in vitro, a redistribution of enzymes occurs between cell particles and cell sap. It is suggested that release of enzyme into the cell sap may be the first stimulus for subsequent enzyme synthesis which occurs after birth.