58497-11-3Relevant academic research and scientific papers
Synthesis of glycosyl phosphates and azides
Sabesan,Neira
, p. 169 - 185 (1992)
Anomerically enriched diphenyl hexopyranosyl phosphate triesters have been prepared from O-alkyl and -acylated hexopyranoses, using diphenyl chlorophosphate and 4-N,N-dimethylaminopyridine. Glycosyl phosphate triesters of D-gluco-, D-galacto-, D-manno, 2-acetamido-2-deoxy-D-gluco-, L-fuco-, and L-rhamno-pyranosyl derivatives have been obtained by this procedure. At temperatures 0° and above, and under thermodynamic control, diphenyl glycosyl phosphates cis to the pyranosyl C-2 substituent are formed predominantly, whereas at low temperatures and under kinetic control, glycosyl phosphate triesters having 2-trans stereochemistry are obtained. The β-glycosyl phosphate triesters of D-glucose and D-galactose derivatives are unstable and undergo anomerization to the α-glycosyl phosphate triesters, in contrast to the stable β-phosphate derivatives of L-rhamnose and D-mannose. These phosphate triesters have been deprotected to glycosyl phosphate triethylammonium salts, suitable for the preparation of other key biological derivatives, such as nucleotide sugars. In addition, the diphenyl phosphate groups at the anomeric center have been displaced by azide togive the glycosyl azides, key intermediates in the synthesis of glycosyl amino acids. Anomerically enriched diphenyl hexopyranosyl phosphate triesters have been prepared from O-alkyl and -acrylated hexopyranoses, using diphenyl chlorophosphate and 4-N,N-dimethylaminopyridine. Glycosyl phosphate triesters of D-gluco-, D-galacto-, D-manno, 2-acetamido-2-deoxy-D-gluco-, L-fuco-, and L-rhamno-pyranosyl derivatives have been obtained by this procedure. At temperatures 0° and above, and under thermodynamic control, diphenyl glycosyl phosphates cis to the pyranosyl C-2 substituent are formed predominantly, whereas at low temperatures and under kinetic control, glycosyl phosphate triesters having 1,2-trans stereochemistry are obtained. The β-glycosyl phosphate triesters of D-glucose and D-galactose derivatives are unstable and undergo anomerization to the α-glycosyl phosphate triesters, in contrast to the stable β-phosphate derivatives of L-rhamnose and D-mannose. These phosphate triesters have been deprotected to glycosyl phosphate triethylammonium salts, suitable for the preparation of other key biological derivatives, such as nucleotide sugars. In addition, the diphenyl phosphate groups at the anomeric center have been displaced by azide to give the glycosyl azides, key intermediates in the synthesis of glycosyl amino acids.
Structure and mechanism of the ER-based glucosyltransferase ALG6
Bloch, Jo?l S.,Pesciullesi, Giorgio,Boilevin, Jérémy,Nosol, Kamil,Irobalieva, Rossitza N.,Darbre, Tamis,Aebi, Markus,Kossiakoff, Anthony A.,Reymond, Jean-Louis,Locher, Kaspar P.
, p. 443 - 447 (2020/03/04)
In eukaryotic protein N-glycosylation, a series of glycosyltransferases catalyse the biosynthesis of a dolichylpyrophosphate-linked oligosaccharide before its transfer onto acceptor proteins1. The final seven steps occur in the lumen of the endoplasmic reticulum (ER) and require dolichylphosphate-activated mannose and glucose as donor substrates2. The responsible enzymes—ALG3, ALG9, ALG12, ALG6, ALG8 and ALG10—are glycosyltransferases of the C-superfamily (GT-Cs), which are loosely defined as containing membrane-spanning helices and processing an isoprenoid-linked carbohydrate donor substrate3,4. Here we present the cryo-electron microscopy structure of yeast ALG6 at 3.0?? resolution, which reveals a previously undescribed transmembrane protein fold. Comparison with reported GT-C structures suggests that GT-C enzymes contain a modular architecture with a conserved module and a variable module, each with distinct functional roles. We used synthetic analogues of dolichylphosphate-linked and dolichylpyrophosphate-linked sugars and enzymatic glycan extension to generate donor and acceptor substrates using purified enzymes of the ALG pathway to recapitulate the activity of ALG6 in vitro. A second cryo-electron microscopy structure of ALG6 bound to an analogue of dolichylphosphate-glucose at 3.9?? resolution revealed the active site of the enzyme. Functional analysis of ALG6 variants identified a catalytic aspartate residue that probably acts as a general base. This residue is conserved in the GT-C superfamily. Our results define the architecture of ER-luminal GT-C enzymes and provide a structural basis for understanding their catalytic mechanisms.
