JBC, Vol. 250, Issue 18, 7272-7276, Sep, 1975
The enediolate analogue 5-phosphoarabinonate as a mechanistic probe for phosphoglucose isomerase
J. M. Chirgwin and E. A. Noltmann
A stable analogue has been prepared of the enediolate anion believed to
occur transiently in the reaction of phosphoglucose isomerase. This
compound, 5-phosphoarabinonate, is the strongest known competitive
inhibitor of the enzyme (Ki = 3 times 10(-7) M below pH 7). A distinctive
pH dependence of binding, also found for two other aldonic acid
omega-phosphates, 6-phosphogluconate and 4-phosphoerythronate, involves
pertubation of a pKa from 7.0 in the free enzyme to 9.0 in the
enzyme-inhibitor complex. This perturbation may reflect a catalytically
advantageous increase in basicity which occurs around the transition state
of the normal enzymatic reaction.