Biosynthesis of lipid-linked oligosaccharides in embryonic liver. Glucosylation of mannose containing dolichyl diphosphate oligosaccharide

Abstract

1. 1. A maximum rate of dolichyl phosphate [ 14C]glucose synthesis from 55-day embryos was achieved at 16nM concentration of exogenous dolichyl phosphate and exceeded about 3 times that without addition of dolichyl phosphate. 2. 2. The highest values of [ 14C]glucose incorporation from UDP-[ 14C]glucose into dolichyl phosphate [ 14C]glucose, dolichyl diphosphate [ 14C]Glc-oligosaccharides and proteins were reached at 5 min time point of incubation of liver microsomes both from embryos and sows. 3. 3. The radioactive incorporation into proteins was about 7-fold higher in liver microsomes from sows compared to that from embryos, probably due to the greater content of acceptor proteins in microsomes from sows. 4. 4. The enzymatic transfer of Glc 3-oligosaccharide from a lipid carrier to endogenous protein acceptor in microsomes from pig embryonic and adult livers was considerably faster than the removal of glucose residues during the initial stages of processing of protein-bound oligosaccharides. 5. 5. One labelled compound was discovered in the Chcl 3-Ch 3Oh-H 2O (1:1:0.3, by vol) extract after incubation of liver microsomes from embryos and sows with UDP-[ 14C]glucose. On the basis of its mobility on the chromatogram it appears to be GlcNAc 2Man 9Glc 3.