A-D-Mannose, 1-phosphate

This enzyme [EC 2.7.7.13], also known as GTP-mannose-1-phosphate guanylyltransferase, catalyzes the reaction of GTP with a-D-mannose 1-phosphate to produce GDP-mannose and pyrophosphate (or, diphosphate). The bacterial enzyme can also use ITP and dGTP as the phospho-ryl donors. 

Furthermore, a-D-mannose-1-phosphate represents a substrate for the enzyme, and the a-mannosyl-maltotetraose is obtained. Supplementary to this result, the a-phosphate of uronic acid was tested, but no enzymatic elongation... 

In section 10.1, we saw that the first hexose to be formed in the fixation of CO2 was D-fructose-l,6-bisphosphate. This sugar phosphate is converted to D-fruc-tose-6-phosphate by a specific phosphatase (reaction 10.3). The keto group can be epimerized by two different enzymes, D-fructose-6-phosphate/D-glucose epimer-ase or D-fructose-6-phosphate/D-mannose epimerase, to form D-glucose-6-phosphate and D-mannose-6-phosphate, respectively (see Fig. 10.5). Both of these sugar phosphates can be converted into their 1-phosphates by reaction with specific mutase enzymes. a-D-Glucose-1-phosphate and a-D-mannose-1-phosphate can then react with UTP and GTP to form UDP-Glc and GDP-Man (see Fig. 10.5). 

Leloir110(a) has described a conversion of D-mannosyl phosphate to D-mannose 6-phosphate by phosphoglucomutase, and here, too, the reaction requires catalytic quantities of a-D-glucose 1,6-diphosphate. The role of the latter is probably to generate a-D-mannose 1,6-diphosphate as follows. 

Fig. 16. Enzymatic synthesis of GDP-a-D-mannose (23) from D-mannose (20) via a-D-mannose-6-phosphate (21) and ot-D-mannose-1 -phosphate (22) with in situ regeneration of ATP. A Hexokinase (EC 2.7.1.1), B Pyruvate kinase (EC 2.7.1.40), C Phosphomannomutase (EC 5.4.2.8), D GDP-Man pyrophosphorylase (EC 2.7.7.13), E inorganic pyrophosphatase (EC 3.6.1.1) [311]...

A D-mannosylphosphate-transferase has been isolated from Saccharomyces cerevisiae X2180 and shown to catalyse the transfer of D-mannose-1-phosphate... 

Immunological studies have confirmed that Bacillus pumilus Sh-17 polysaccharide cross-reacts with meningococcal group A polysaccharide. The cross-reaction is ascribed to the presence of residues of 2-acetamido-2-deoxy-D-mannose 1-phosphate in both polysaccharides. Two polysaccharides isolated from two strains of Neisseria meningitidis group C are identical to the group C antigen, but they differ in the extent of hydrolysis by neuraminidase. ... 

As 2-amino-2-deoxy-D-mannose is tumorstatic and 2-acetamido-2-deoxy-D-mannose 6-phosphate is an obligatory intermediate in the biosynthetic pathway to sialic acid, displacement of the essential OH-6 with a fluorine atom should be interesting from the biological viewpoint. 2-Acetamido-1,3,4-tri-0-acetyl-2,6-dideoxy-6-fluoro-D-mannopyranose (see Table 111 in Section 11,3) and its O- and A,0-deacetyl derivatives were prepared the first compound showed weak anticancer activity. 

It is D-fructofuranose, not D-fructopyranose, that is utilized, at least by bakers yeast.303,304 As with D-glucose, the initial step in the intracellular utilization of either D-fructofuranose305 or D-mannose is phosphorylation by the constitutive hexokinase306 (see Ref. 307 for a review). The D-fructose 6-phosphate formed is an intermediate of both the glycolytic pathway and the pentose cycle. D-Mannose phosphate isomerase (EC 5.3.1.8) effects the conversion of D-mannose 6-phosphate into D-fructose 6-phosphate,308,309 or D-mannose 6-phosphate is epimerized to D-glucose 6-phosphate.308... 

GDP-Man regeneration system starting from Man-l-P has been report by Wong s gcoup(9). As the Fru-6-P is inexpensive to obtain, we developed a new regeneration padiway from Fru-6-P with all recombinant enzymes. As shown in Scheme 4, the cycle comprises of three key enzymes D-mannose-6-phosphate isomerase (PMI, EC 5.3.1.8), phosphomannomutase (PMM, EC 5.4.2.S) and... 

Aldoses react with ATP in a phosphotransferase-catalyzed reaction (C 1.1) either to sugar-l-phosphates, e.g., D-galactose-l-phosphate and L-arabinose-1-phosphate, or to sugar-co-phosphates, e.g., D-glucose-6-phosphate (Fig. 27), D-mannose-6-phosphate, D-galactose-6-phosphate, and D-ribose-5-phosphate. Aldose-l-phosphates may also be formed from co-phosphates by mutases (Fig. 27) with 1,co-diphosphates as intermediates. 

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