5'-Nucleotidase activity in adult and fetal rabbit lungs

5'-Nucleotidase was assayed in the membrane fractions isolated from rabbit lung homogenate. The enzyme activity was measured from the rate of hydrolysis of [U-14C]cytidine 5'-monophosphate (CMP). The optimal pH of the rate of hydrolysis is around 8.0 and the enzyme activity is stimulated by Mg2+. The apparent Km and Vmax of the enzyme in the microsomal fraction for CMP were 3.33 mM and 1.43 mumol/min/mg protein, respectively. During lung development the enzyme activity increased moderately at late gestational ages and reached its maximum level in adults (p less than 0.001). The developing profile of 5'-nucleotidase activity is similar to the developing pattern of the CMP content in rabbit lungs.