GDP-Sugars

In situ recycling methods for GDP-Fuc are not yet optimized for preparative-scale synthesis. This is mainly because of difficulty obtaining adequate quantities of the key biosynthetic enzymes. GDP-Man pyrophosphorylase, GDP-synthesizing enzymes , fucokinase, and GDP-Fuc pyrophosphorylase are currently not available commercially. 

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Involved in the transfer of sugar residues from GDP-sugar to acceptor molecules in the formation of glycans in fungi... 

Cell lysates from mutant strains of X. campestris were incubated with radiolabelled UDP[14C] glucose or GDP[,4C] mannose, the other sugar nudeotide substrates being unlabelled. The reaction mixture was then divided into lipid and soluble fractions. Where would you expect the radiolabel to be found and what produd, if any, would you expert from strains with defidendes in the following genes ... 

Mannose Hexose Man GDP-Man Common sugar in N-linked glycoproteins. 

UDP-a-D-Gal UDP-a-D-GlcNAc GDP-a-D-Man GDP-P-l-Fuc CMP-Neu5Ac In situ regeneration systems for nucleotide sugars UDP-a-D-Glc combinatorial biocatalysis [44-49]... 

Figure 3. Gel filtration of alkali-soluble xyloglucan on columns (95 x 1.5 cm) of Sepharose CL-6B. Pea microsomal membranes were incubated for various periods with GDP-[14C]fucose and unlabelled sugar nucleotides. Products were eluted with 0.1 M NaOH in 1 ml fractions. Molecular weights of dextran markers, 1 = 264000 D 2 = 70000 D 3 = 40000 D 4 = 10600 D Glc=glucose. Redrawn from Camirand and Maclachlan (20).

C. Formation of deoxyribonudeotides by reduction of the 2 -hydroxyl group of the ribose sugars on the ribonucleoside diphosphates ADP and GDP is catalyzed by ribonucleotide reductase (Figure 10-3). 

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