Mechanistic implications of the pH independence of inhibition of phosphoglucose isomerase by neutral sugar phosphates

John Chirgwin, T. F. Parsons, E. A. Noltmann

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

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 languageEnglish (US)
Pages (from-to)7277-7279
Number of pages3
JournalJournal of Biological Chemistry
Volume250
Issue number18
StatePublished - 1975
Externally publishedYes

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Sugar Phosphates
Glucose-6-Phosphate Isomerase
Sorbitol
Substrates
Phosphates
Enzymes
erythrose 4-phosphate
arabinose 5-phosphate
erythritol 4-phosphate

ASJC Scopus subject areas

  • Biochemistry

Cite this

Mechanistic implications of the pH independence of inhibition of phosphoglucose isomerase by neutral sugar phosphates. / Chirgwin, John; Parsons, T. F.; Noltmann, E. A.

In: Journal of Biological Chemistry, Vol. 250, No. 18, 1975, p. 7277-7279.

Research output: Contribution to journalArticle

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abstract = "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.",
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