DEVELOlXENTAL AND ADAPTIVE CHARACTERISTICS IN THE RAT LIVER

Galactokinase catalyzes the formation of cy-n-galactose l-phosphate from adenosine triphosphate and n-galactose (1, 2) and is the first enzyme in a series by which galactose enters the varied pathways of glucose metabolism (3, 4). Although galactokinase has been studied extensively in various microorganisms, in mammalian tissues investigations have been limited to confirmation of its presence in liver, brain, and erythrocytes (3, 5-7). Studies of mammalian galactokinase have been undertaken in order to evaluate the participation of the enzyme in the regulation of galactose metabolism, especially in the young in which there is a critical dependence on dietary galactose. The present work describes certain properties of young and adult rat liver galactokinase and suggests the presence of at least two different hepatic enzymes capable of phosphorylating galactose. Galactokinase activity was also measured in several other rat tissues. Changes occurring during development and those induced by dietary treatment are described.