Journal of Protein Chemistry

, Volume 2, Issue 5, pp 363–370 | Cite as

Dependence of reactivity and cooperativity in normal human erythrocyte glucose-6-phosphate dehydrogenase on ionic strength, pH, and temperature

  • Suara A. Adediran


The steady-state kinetics of the binding reaction of NADP+ to normal human erythrocyte glucose-6-phosphate dehydrogenase were studied as a function of pH, ionic strength, and temperature. The interaction coefficient obtained according to the Hill equation increases with increase in pH, ionic strength, and temperature. The observed variation of cooperative interaction is interpreted in terms of an increase in the percentage of the dimer as these environmental parameters increase. Activation energy decreases with increase in pH, the activation energy at the lowest pH being almost halved at the most alkaline pH. This behavior is explained in terms of a differential reactivity between the dimeric and tetrameric forms of the enzyme. The observation of cooperative and more reactive dimer is postulated to be a regulatory mechanism by the cell for shifting the equilibrium from one quaternary structure to the other depending on the need for NADPH.

Key words

reactivity cooperativity human erythrocyte glucose-6-phosphate dehydrogenase 


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Copyright information

© Plenum Publishing Corporation 1983

Authors and Affiliations

  • Suara A. Adediran
    • 1
  1. 1.Department of ChemistryUniversity of IbadanIbadanNigeria

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