Presence of asialo GM1 and glucosylceramide in the intestinal mucosa of mice and induction of fucosyl asialo GM1 by conventionalization of germ-free mice.

Two major neutral glycolipids of the intestinal mucosa were purified by a series of column chromatographies and the structures were determined to be glucosylceramide and asialo GM1 by gas liquid chromatography. The carbohydrate structure of asialo GM1 was also confirmed from the reactivity of the glycolipid to rabbit anti-asialo GM1 antibody by an enzyme linked-immunosorbent antibody. The ceramide portion of both glycolipids had an extremely hydrophilic nature and more than 90% of the ceramide was composed of phytosphingosine and alpha-hydroxy fatty acids. In the previous paper we reported that the induction of a fucolipid in the microvillus membrane of mouse intestinal mucosa by conventionalization was observed on monitoring the incorporation of radiolabeled fucose in vivo. A fucoglycolipid having the same mobility on an autoradiogram as the fucolipid labeled in vivo was produced by in vitro incubation of intestinal asialo GM1 and GDP-[14C]fucose with the mucosal homogenates. Moreover, asialo GM1 prepared from brain gangliosides exhibited a similar ability to accept fucose and it was converted to fucosyl asialo GM1 which moved faster than the product from intestinal asialo GM1. The difference is considered to be due to the ceramide composition. These results suggest that conventionalization can induce the fucosyl asialo GM1 in the microvillus membrane probably through the induction of fucosyltransferase. Understanding the molecular mechanism of interaction between the physiological flora and host is the matter of further study.