PMID: 6985800Jan 11, 1980Paper

Effects of free magnesium and alkali ions on the conformation and glucose-binding strength of yeast hexokinase isozymes

Biochimica Et Biophysica Acta
G E Norton, I Feldman

Abstract

Titrations of the tryptophan fluorescence of yeast hexokinase (ATP:D-hexose 6-phosphortransferase, EC 2.7.1.1.) isozymes P-I (A) and P-II (B) were performed with Mg2+, Li+, Na+ and K+ as titrant in absence and in presence of glucose, and vice versa, at pH 8.3 and 5.5 at 20 degrees C. Mg2+ quenches the fluorescence of surface tryptophan primarily and does so by producing a conformational change which alters the microenvironment of the tryptophan. For both isozymes Mg2+ exerts a specific ion effect, i.e. significantly larger than the ionic strength (I) effect, which enhances the glucose quenching by causing a conformation change which increases the glucose-binding constant. For the P-I isozyme glucose binding exhibits positive cooperativity at both pH 8.3 and 5.5 when the ionic strength (I) is low, i.e. significantly larger than the ionic strength (I) effect, which enhances the glucose quenching by causing a conformation change which increases the glucose-binding constant. For the P-I isozyme glucose binding exhibits positive sooperativity at both pH 8.3 and 5.5 when the ionic strength (I) is low, i.e. 0.04 or less, regardless of which of the above four cations is present. For P-II, however, glucose binding is non-cooperative at ...Continue Reading

References

Dec 20, 1978·Biochimica Et Biophysica Acta·D C Kramp, I Feldman
Dec 1, 1977·Proceedings of the National Academy of Sciences of the United States of America·A NomotoE Wimmer
Oct 1, 1978·Proceedings of the National Academy of Sciences of the United States of America·W S Bennett, T A Steitz
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Mar 1, 1962·Biophysical Journal·G EISENMAN

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Citations

Dec 1, 2007·Clinical Science·Federica I Wolf, Valentina Trapani
Nov 10, 2017·Scientific Reports·Robert A Gatenby, B Roy Frieden

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