Developmental aspects of the lysosomal apparatus. Membrane affinity of N-acetyl-beta-D-glucosaminidase in developing rat liver.

The affinity of N-acetyl-beta-D-glucosaminidase by membranes of liver was studied in rats of different ages including fetuses at day 18 of gestation. It was found that membrane bound enzyme activity, extractable with 0.6 KCl, increases from fetal life to adulthood reaching a peak 9 days after birth. In binding assays it was found that the enzyme of fetal, 9 days old, or adult rat has high affinity for membranes of the corresponding age. These bindings were saturable and with a similar KD, but the number of receptor sites was lowest in the fetal stage, and reached a peak 9 days after birth. The fetal enzyme did not bind to adult membranes. These results suggest that the transport system of hepatic lysosomal enzymes undergoes post-natal changes which are synchronic with other parameters of lysosomal apparatus maturation studied by us and other authors as total enzyme activity and intracellular digestion of macromolecules.