Résumé : The 1H NMR spectrum obtained with the α- and β-anomers of d-[1-2H]fructose 6-phosphate generated from d-glucose 6-phosphate sequentially exposed in D2O to phosphoglucoisomerase, phosphoglucoisomerase, phosphofructokinase and fructose-1,6-diphosphatase differed from that recorded when the deuterated ketohexose phosphate was produced from d-mannose 6-phosphate sequentially exposed in D2O to phosphomannoisomerase, phosphofructoctokinase and fructose-1,6-diphodphatases. The identification of the 2 isotopomers of d-fructose 6-phosphate by 1H NMR spectroscopy provides a new tool to assess the relative extent of interconversion of hexose phosphates in the reactions catalyzed by phosphoglucoisomerase and phosphomannoisomerase, respectively. © 1991.