Maturation decline in lactase activity is complex phenomenon which is either due to shift in lactase synthesis and processing to the inactive 100Kda and Increased degradation of the lactase activity of 130kda subunit, or decline in the enterocyte life span.lactase phlorizin hydrlase shifts from a high sialylation status during weaning to high fucosylation level in adult rats. The activities of brush border lactase were assayed. sialic acid and fucose were estimated. Membrane protein were resolved by SDS‐PAGE on to nitocellulose paper/PVD membrane and immunostained with polyclonal antibodies against lactase. Total RNA was isolated and transfered RNA to nylon membrane.Determination of fucose to sialic acid ratio revealed close parllelism between fucosylation and sialylation of microvillus membranes with decline in intestinal lactase activity with development age in rat. Upstream region of prolactase gene, suggesting the absence of functional role in mature lactase mRNA and also mRNA is poorly translated to active lactase in the adult intestine which may be due to its interaction with 100kda protein product of prolactase hydrolysis. Western blot analysis revealed the presence of 100kda protein in rat intestine during postnatal development.