The metal-binding sites of glycose phosphates

In aqueous solution, the reducing sugar phosphates D-arabinose 5-phosphate, D-ribose 5-phosphate, D-fructose 1,6-bisphosphate, D-fructose 6-phosphate, D-glucose 6-phosphate and D-mannose 6-phosphate provide metal-binding sites at their glycose core on reaction with Pd-II(en) or M-III(tacn) residues (M = Ga, Co; en = ethylenediamine, tacn = 1,4,7-triazacyclononane). The individual species were detected by one-and two-dimensional NMR spectroscopy. The coordination patterns are related to the metal-binding modes of the respective parent glycoses. In detail, ribo-and arabinofuranose phosphate favour kappa O-1,O-3 coordination, whereas the ketofuranose core of fructose phosphate and fructose bisphosphate provides the kappa O-2,O-3 chelator thus maintaining the configuration of the respective major solution anomer. On palladium excess, D-fructose 6-phosphate is metallated twice in a unique kappa O-1,O-3:kappa O-2,O-4 metallation pattern. Dimetallation is also found for the aldohexose phosphates. A mixed glycose-core-phosphate chelation was detected for Pd-II(en) and M-III(tacn) residues with M = Al, Ga in the pH range just above the physiological pH for the D-fructose 1,6-bisphosphate ligand. The results are discussed in relation to D-fructose-1,6-bisphosphate-metabolism in class-II aldolases.