Relationship between gamma-glutamyl transpeptidase activity and sialic acid content in some organs and brain regions of the developing rat.

The activity of gamma-glutamyl transpeptidase (GGT) and the sialic acid (SA) content were found to be specific in five brain regions of 7- and 50-day-old rats. While a low GGT activity was accompanied by high sialylation in the whole brain a high GGT activity and low sialylation were observed in kidney and pancreas. Similar findings were obtained for some brain regions investigated. However, the developmental differences were not characterized by such relationship. Concanavalin A affinity chromatography of GGT from brain of 7- and 50-day-old rats revealed no remarkable changes in GGT sialylation although the enzyme activity is almost 3 times higher in brain membranes of the older group. It can be concluded that in spite of an apparent relationship between GGT activity and membrane sialylation, the amount of SA linked to the GGT molecule is not related to differences in enzyme activity.