Regional and cellular localization of glycosyltransferases in rat small intestine. Changes in enzymes with differentiation of intestinal epithelial cells.

Optimal assay conditions were determined for four glycosyltransferases in rat small intestinal mucosal homogenates and the regional distribution and cellular localization of these enzymes was studied. For each glycosyltransferase, similar levels of activity were found in duodenal, proximal jejunal and distal ileal segments; activities of the galactosyltransferases were lower in the distal jejunal-proximal ileal segment. Planar section studies indicated that the undifferentiated crypt cells had significantly higher levels of sialyltransferase activities in the jejunum and ileum than the mature villus cells. A similar crypt to villus gradient was found for a galactosyltransferase in the ileum. These data suggest that glycoprotein synthesis may be active in the undifferentiated crypt cells and that certain glycosyltransferases may serve as marker enzymes for cellular differentiation in the intestine.