ADPglucose pyrophosphorylase: Evidence for a lysine residue at the activator site of the Escherichia coli B enzyme |
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Authors: | Thomas Haugen Armana Ishaque Jack Preiss |
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Affiliation: | Department of Biochemistry and Biophysics University of California Davis, California 95616 USA |
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Abstract: | Pyridoxal-P can be covalently linked to B ADPglucose pyrophosphorylase by reduction with sodium borohydride. The modified enzyme is almost fully active when less than 1 mole of pyridoxal-P is incorporated per mole of enzyme subunit and is no longer dependent on the presence of allosteric activators in reaction mixtures for high activity. The allosteric activators, fructose-P2 or hexanediol 1,6 bisphosphate, decrease the incorporation of pyridoxal-P into enzyme suggesting that the pyridoxal-P is linked at or near the allosteric activator binding site. Acid hydrolysis of the modified enzyme yields pyridoxyllysine suggesting that the epsilon amino group of lysine is functional in the binding of the allosteric activators of the enzyme. |
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