The activity of galactose-1-phosphate uridyltransferase and galactokinase in human fetal organs

The activity of galactose-1-phosphate uridyltransferase (transferase) and galactokinase in several organs from human fetuses 7-28 weeks old was measured by using radioactive substrates and column chromatography for product identification. The specific activity of transferase and galactokinase increased with gestational age and reached, at the 28th week, a maximal level of 30.0 and 7.9 nmol/min/mg protein (units) in liver, 4.7 and 2.5 units in kidney, 6.0 and 4.0 units in lung, 6.7 and 2.9 units in spleen, 5.2 and 2.6 units in cardiac muscle, and 4.0 and 1.4 units in skeletal muscle, respectively. The activity in brain, on the other hand, remained quite constant with 1.2 units in the case of transferase and 0.5 units in the case of galactokinase during this period. The activities of both enzymes in the liver of children were slightly lower than the highest fetal level during the period of pregnancy studied. Galactokinase activity in fetal erythrocytes was approximately 4 times higher and the transferase activity approximately 30% higher than in adults. The Km value of fetal liver transferase for galactose-1-phosphate was found to be 0.330-0.357 mM and that of galactokinase for galactose, 0.265-0.277 mM.