In contrast to the strongly pH dependent inhibition of phosphoglucose isomerase by substrate analogues with a free carboxyl group, inhibition of this enzyme by neutral sugar phosphates is essentially invariant between pH 7 and 9. Competitive inhibition constants for glucitol 6 phosphate (40 μM), arabinose 5 phosphate (50 μM), and erythritol 4 phosphate (100 μM) were found to be of the same order of magnitude as that reported previously for substrate binding constants (50 to 240 μM). The unique exception is erythrose 4 phosphate whose K(i) (0.7 μM, independent of pH) reflects a tightness of binding similar to that found at pH values near or below neutrality for the transition state analogue 5 phosphorarabinonate. The pH independence of inhibition by erythrose 4 phosphate and other neutral sugar phosphates may reflect a mode and locus of binding to phosphoglucose isomerase different from that of the aldonate inhibitors.
|Original language||English (US)|
|Number of pages||3|
|Journal||Journal of Biological Chemistry|
|State||Published - Dec 1 1975|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology