Mannose, biosynthesis

Maltose, l- 4- -link in, 998 molecular model of, 998 mutarotation of, 998 structure of, 998 Manicone, synthesis of. 805 Mannich reaction. 915 Mannose, biosynthesis of, 1011 chair conformation of, 126 configuration of, 982 molecular model of, 126 Margarine, manufacture of, 1063 Markovnikov. Vladimir Vassilyevich. 192... 

Wu BY, Zhang Y-X, Zheng R, Guo C-W, Wang PG. Bifunctional phosphomannose isomerase/GDP-D-mannose pyrophosphorylase is the point of control for GDP-D-mannose biosynthesis in Helicobacter pylori. FEBS lett 2002 519 87-92. 

GDP-mannose pyrophosphorylase (GMP, EC 2.7.7.13). The recombinant bifimctional PMI/GMP (phosphomannose isomerase/GDP-D-mannose pyrophosphorylase) from Helicobacter pylori has been cloned and overexpressed in E. coli (21), The bifunctional enzyme PMI/GMP catalyzes both the first and third steps of GDP-D-mannose biosynthesis from D-fructose-6-phosphate. In addition, PMM of H. pylori was also cloned and overexpressed (21), The system was coupled with a truncated al,2-mannosyltransferase (ManT catalytic domain, Saccharomyces cerevisiae) to synthesize the mannosyloligosaccharides (not published). 

The biosynthesis of Kdo and neuraminic acid is known to involve enol-pyruvate phosphate and D-arabinose or 2-acetamido-2-deoxy-D-mannose, respectively. Nothing is known about the biosynthesis of all the other glycu-losonic acids. One interesting problem is, for example, whether the two 5,7-diamino-3,5,7,9-tetradeoxynonulosonic acids are synthesized analogously to neuraminic acid, from a three- and a six-carbon fragment, by modification of neuraminic acid on the sugar nucleotide level, or by a third, less obvious route. 

Figure 47-7. Pathway of biosynthesis of dolichol-P-P-oligosaccharide. The specific linkages formed are indicated in Figure 47-8. Note that the first five internal mannose residues are donated by GDP-mannose, whereas the more external mannose residues and the glucose residues are donated by dolichol-P-mannose and dolichol-P-glucose. (UDP, uridine diphosphate Dol, dolichol P, phosphate UMP, uridine monophosphate GDP, guanosine diphosphate M, mannose G, glucose.)...

Metabolic labelling of cells with [2-3H]mannose fails to detect deficiencies in the very early onset of LLO biosynthesis as in CDG-Ij and CDG-Ik (Fig. 4.5.1). In this case,... 

Defects in the early steps of LLO biosynthesis (Fig. 4.5.1) lead to an accumulation of shortened LLO that escape the extraction procedure described above (e.g. CDG-Ik). Moreover, defects in the initiating steps of LLO biosynthesis, such as the addition of the two glucosamine residues and the first mannose residue, are missed by metabolic labelling with [2-3H]mannose. In this case it is necessary to label fibroblasts with [6-3H] glucosamine. 

Scheme 1. — Reactions Involved in the Biosynthesis of D-Mannan from GDP-Mannose. [The acceptor lipid in the reaction, undecaprenyl phosphate, is designated as follows ]...

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