Developmental Changes in Intestinal Glycosyl-Transferase Activities

Abstract

ABSTRACT. The carbohydrate composition of some intestinal glycoproteins has been demonstrated previously to be modified during development. To evaluate the role of the enzymatic mechanisms of glycosylation, the activities of three soluble and microsomal glycosyl-transferases were studied during postnatal development in rat intestinal mucosa. Nonexistent as soluble forms in the cell sap from suckling rats, the membrane-bound N-acetylgalactosaminyl-, sialyl-, and fucosyl-transferases showed different activities in microsomal fractions before weaning. The Nacetylgalactosaminyl-transferase activity was constant whereas the sialyl-transferase activity, which was maintained at a rather high level until the age of 2 wk, decreased just before weaning, while the fucosyl-transferase activity declined progressively from birth to weaning. After weaning, the three enzymatic activities progressively enhanced until adult age. Their variable behaviors on several glycoprotein acceptors may suggest the presence of several sialvl-and fucosvl-transferases with differences in soecificities, varying " I I different ways according to age. Such developmental modifications in intestinal glycosylation patterns may be linked with certain transformation ohserved in the carbohydrate level of mucus or membranebound glycoproteins and related to the profound modifications in nutritional status at the weaning period. (Pediatr Res 22: 250-256, 1987) The glycoconjugates play a prominent part in the small intestinal tract as mucus and cellular membrane components. The pre-and postnatal developmental patterns of digestive glycoprotein enzymes [such as sucrase, nialtase, isomaltase, alkaline phosphatase, or aminopeptidase (1-41 have been studied with regard to the level of enzyme activity. However, in terms of carbohydrate composition, little is known about the structure of such enzymes, except for y-glutamyl-transferase (5) and alkaline phosphatase (6, 7) which have been demonstrated to possess differences in the sialic acid content of fetal and adult-type enzymes.Modifications in the electrophoretic behavior (I) and in the glycosylation of the microvillus membrane glycoproteins (8-10) have been noted. Age-related differences in the types of mucus glycoproteins synthesized in the small intestinc were also demonstrated (I I). In all cases, the variations observed between Received September 8, 1986: accepted March 27, 1987 ' Charge dc Recherches au Centre National de la Recherche Scientifique. 2 newborn and adult animals were in glycoprotein fucosylation or sialylation. Moreover. the biosynthesis and the intracellular transport of glycoproteins were modified in rat duodenal absorptive cells as a function of age (12).Some intestinal glycosyl-transferases, responsible for the biosynthesis of carbohydrate chains of the glycoconjugates, have been well characterized ( 1 3-15). The intestinal glycosylation processes are known to depend on different factors: distribution along the intestinal tract (16) and along the crypt-to-villus axis (17, 18), admini...

Glutamate Transporter Protein Subtypes Are Expressed Differentially during Rat CNS Development

“…Developmental-dependent changes in glycosylation have also been observed with dopamine transporters during postnatal maturation (Patel et al, 1994). The developmental regulation in glycosylation may be explained by the availability of different glycosyltransferases during ontogenesis (Biol et al, 1987); yet, the selectivity for this change in the post-translational modification of GLAST (but not other glutamate transporters) is unclear. In vitro studies have revealed that the extent of N-linked glycosylation has a negligible effect on the transport activity of GLAST expressed in Xenopus oocytes (Conradt et al, 1995).…”

Influence of spermine on intestinal maturation of the glycoprotein glycosylation process in neonatal rats

“…Indeed, the increase in intestinal spermine level at weaning paralleled that of fucosyltransferase activity that is naturally observed at this period [8], and the appearance of fucoproteins in the brush border membranes [11].…”

“…A shift from a high sialylation before weaning to a high fucosylation of the glycan chains after weaning has been demonstrated in glycoproteins of purified brush border membranes [2][3][4] and in mucins [5] by various techniques, as well as in the apical and basolateral membranes of the epithelial cells by lectin cytochemistry [6]. This shift is accompanied by a parallel decline in the activity and the mRNA level of an α-2,6-sialyltransferase from birth to weaning time [7][8][9] and by a large increase in the activity of an α-1,2-fucosyltransferase just after weaning [10,11].…”

Intestinal Absorption of Macromolecules and Epithelial Cell Surface Glycosylation in Suckling Rats Nursed on Mothers Fed Low-Protein Diet-I

“…The microvillus membrane (MVM) lining the enterocytes contains con siderable amounts of carbohydrates [4], We have previously shown that surface-reactive carbohydrates, in particular sialic acid and fucose, undergo striking modifications dur ing postnatal development in rat intestine [5,6]. During early suckling period, the membrane is rich in sialic acid and contains low levels of fucose but the pattern is re versed on weaning [6], Biol et al [7,8] have described that the quality as well as the quantity of diet affects the glycosyl-transferase levels in intestine. Since milk is the sole source of nutrition for the developing pups during the suckling period and the composi tion of milk is altered in response to changes in the maternal nutrition [9,10], we studied the effect of feeding low-protein (LP) diet (8% protein) to lactating rats on the absorp tion of 125I-labelled proteins and the glycosy lation of intestinal microvillus membrane in suckling rats.…”