Pulmonary and hepatic activities of membrane-bound enzymes in man and rat.

The lung of adult man contains several times more 5'-nucleotidase (EC 3.1.3.5), alkaline phosphatase (EC 3.1.3.1) and gamma-glutamyl-transpeptidase (EC 2.3.2.2) per gram than does that of the 12- to 16-week fetus. In rat lung, too, there is a drastic developmental rise in these activities. Opposite changes in two of the enzymes occur during hepatic differentiation: alkaline phosphatase decreases in the rat, and gamma-glutamyl-transpeptidase is ten times higher in the fetal than in the adult liver of both species.