Mutarotation 9-phosphate

Bailey et al., 1970. The reference intermolecular reaction is the phosphate-catalysed mutarotation of D-glucose under the same conditions... 

The presence of sugars and salts can also affect the rate of mutarotation. Although the effect is small in dilute solutions, a combination of salts equal to that found in solution in milk nearly doubles the rate of mutarotation (Haase and Nickerson 1966). This catalytic effect is attributed primarily to the citrates and phosphates of milk. The presence of high levels of sucrose, on the other hand, has the opposite ef-... 

The rapid spontaneous mutarotation of glucose-6-phosphate has been shown to result from an intramolecular catalysis of the reaction by the phosphate group at carbon 6 (81). The cleavage of glucose into three carbon fragments, which is essentially a reversal of the aldol condensation reaction, requires the ketohexose as substrate. The necessary isomerization reaction to form the ketohexose then uses the open-chain form intermediate of the mutarotation reaction. Salas et al. (80) have speculated that the enhanced mutarotation of glucose-6-phosphate may thus have been the key requirement which led to the evolution of the phosphorolytic pathway for glucose metabolism. 

Phosphorylation of XLVII with phosphorus oxychloride in pyridine solution, followed by hydrolysis to remove the methyl and isopropylidene residues, gave D-ribose 5-phosphate (XLVIII) which, as its barium salt, was found to be identical with the barium salt of the D-ribose phosphate from inosinic acid. By way of further confirmation of the structure of D-ribose 5-phosphate, Levene, Harris and Stiller129 showed that in methanolic hydrogen chloride solution both the natural and synthetic material mutarotated in a manner characteristic of a sugar which can form only a furanoside. 

The 5-0-a-L-rhamnopyranosyl derivative of KDO and KDO 7-(2-aminoethylphosphate) have both been isolated from the inner core region of the lipopolysaccharide (LPS) of E.coli K12. The syntheses of KDO-7-phosphate and 7-(2-acetamidoethyl phosphate) have been carried out by phosphorylation of an appropriately-protected derivative. It has been shown that in solution KDO 8-phosphate exists as a mixture of a-pyranose (66%), P-pyranose (3%), a-furanose (19%) and P-furanose (12%) forms. By use of the two isomeric 2-deoxy analogues of KDO 8-phosphate it was shown that KDO 8-phosphate phosphatase is speciflc for the a-pyranose form of the substrate, so that a mutarotation must be involved before the next stage in the formation of LPS, since CMP-KDO synthetase is specific for the P-pyranose form of KDO. 0 Other references to 2-deoxy-KDO and 2-deoxy-NeuNAc can be found in Section 1 of this Chapter. 

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