Affinity Labeling of Phosphoglucose Isomerase by 1,2-Anhydrohexitol-6-phosphates

Abstract 1,2-Anhydro-d-mannitol-6-P rapidly inactivates phosphoglucose isomerase and becomes covalently bound in ester linkage to a glutamate residue. Protection by a competitive inhibitor, saturation kinetics, and strict stoichiometry of alkylation indicate reaction at the active site only. The Vmax of inactivation shows a pH dependence similar to the catalytic Vmax, pK1 = 6.3, pK2 = 9.9. 1,2-Anhydro-l-iditol-6-P and 1,2-anhydro-d-glucitol-6-P also inactivate, possibly at the same residue, but at only 2% of the rate of the mannitol compound.