Anomerization of glucose 6-phosphate: catalysis by phosphoglucose isomerase. |
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Authors: | K J Schray E E Howell |
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Institution: | Department of Chemistry and Center for Health Sciences, Lehigh University, Bethlehem, Pennsylvania 18015 U.S.A. |
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Abstract: | The anomerase (1-epimerase) activity of phosphoglucose isomerase (d-glucose 6-phosphate ketol-isomerase EC 5.3.1.9) has been studied. The pH-Vmax profile, assayed by two different methods, shows a dependence on two ionizable groups in the enzyme with pK values of 7.0 and 9.3 at 0 °C. Additionally, an unusual reversal of the basic leg of the normal profile to yield a large increase in Vmax is observed above pH 9.5. Deuterium solvent isotope effects of are observed for isomerase and anomerase activities respectively. An anomerase mechanism similar to noncatalyzed anomerization is postulated with a discussion of the catalytic groups involved. |
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