Phospho sugars

Horie S, Kubo Y (2009) Fluorescence-based indicator displacement assay for phospho-sugar detection using zinc(II) dipicolylamine-appended phenylboronic acid. Chem Lett 38 616-617... 

The acidic pocket coordinates two Mg ions jointly between the nucleic acid substrate and the catalytic acidic residues of the enzyme (Fig. 1). This idea was based on the proposition of Steitz (the two-ion model), which concerns the reaction chemistry of exonuclease activity of DNA polymerase (18). This coordination enhances nucleophilic attack of the nucleic acid phospho-sugar backbone and guarantees substrate recognition and catalytic specificity (16). 

This hydride shift reaction mechanism is quite different from the base-catalyzed enolization mechanism proposed for phospho sugar isomerases such as triosephos-phate isomerase which generally do not require a metal ion for activity12261. 

In addition to the naturally occurring deoxy, amino, and phospho sugars, other kinds of esters, ethers, and substituted carbohydrates (carbohydrates with hydroxyl and/or hydrogen replaced by other groups), can be chemically or enzymatically synthesized (see Chapter 4). 

All these esters are variously described as sugar phosphates or phospho-sugars. In each of them only one of the three hydroxyl groups of phosphoric acid has been bound, and they are acidic compounds. The process by which they are formed is termed phosphorylation (p. 107). 

Another example from the carbohydrate chemistry (Scheme 47.31) ° illustrates the fact that, as for the addition to a carbonyl group (cf. Scheme 47.10 vs. Schemes 47.11 and 47.12), reactions outside the sugar ring proceed with much lower stereoselectivity, leading to a mixture of products. Nevertheless, the synthesis employs an interesting strategy toward phospho-sugars, and all the diastereomers of the final product 128 could be purified and characterized by NMR spectroscopy. 

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