A biochemical chimera suggesting the existence of at least two dolichol-P-glucose:dolichol-P-P-oligosaccharide glucosyltransferases.
As previously reported, incubation of liver dolichol-P, UDP-[14C]Gal, and a particulate preparation of Acetobacter xylinum leads to the synthesis of dolichol-P-[14C]Gal (P. Romero, R. Garcia, and M. Dankert (1977) Mol. Cell. Biochem. 16, 205-212). It is now reported that upon incubation of the latter with rat liver microsomes, [14C-galactose]-Gal1Man9GlcNAc2-P-P-dolichol and [14C-galactose]Gal1Glc1Man9GlcNAc2-P-P-dolichol are formed. The galactosyl residues appeared to be (1,3)-linked in the same positions as the glucose units in the respective physiological compounds. No lipid-linked Gal1Glc2Man9GlcNAc2 was formed, thus strongly suggesting the presence of at least two dolichol-P-Glc:dolichol-P-P-oligosaccharide glucosyltransferases, only one of which is able to use dolichol-P-Gal as substrate. Incubation of the galactosylated dolichol-P-P derivatives with rat liver microsomes led to the transfer of the oligosaccharides to microsomal proteins. No endogenous, membrane-bound glycosidases were able to remove the galactose residues but mannose units were excised by endogenous neutral mannosidases.
Iñón de Iannino
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Instituto de Investigaciones Bioquímicas, Fundación Campomar, Buenos Aires, Argentina.
Dankert
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MA
D000107:Acetylation; D000118:Acetylglucosaminidase / Q000494:pharmacology; D000818:Animals; D002678:Chimera; D002854:Chromatography, Paper; D005964:Glucosyltransferases / Q000302:isolation & purification* / Q000378:metabolism; D006019:Glycolysis; D006023:Glycoproteins / Q000378:metabolism; D008361:Mannosidases / Q000494:pharmacology; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008745:Methylation; D008862:Microsomes, Liver / Q000201:enzymology*; D010504:Periodic Acid / Q000494:pharmacology; D051381:Rats; D043323:alpha-Mannosidase
D006023:Glycoproteins; D010504:Periodic Acid; C009288:metaperiodate; D005964:Glucosyltransferases; C054676:dolichol phosphate glucose-dolichol diphosphate oligosaccharide glucosyltransferase; D008361:Mannosidases; D043323:alpha-Mannosidase; D000118:Acetylglucosaminidase; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase