Thermodynamic study of magnesium ion binding to alpha-amylase
Saboury, A.A.; Ghasemi, S.; Dahot, M.U.
Indian Journal of Biochemistry and Biophysics 42(5): 326-329
2005
ISSN/ISBN: 0301-1208 PMID: 23923542 Document Number: 589849
The interaction of alpha-amylase (from Bacillus amyloliquefaciens) with Mg2+ ion was studied using UV spectrophotometric and isothermal titration calorimetric (ITC) methods at 27 degrees C in 30 mM Tris buffer solution at pH = 7.0. The binding isotherm for metal-protein interaction was easily obtained by carrying out ITC experiment at two different concentrations (2 microM and 50 microM) of the protein. Alpha-Amylase had eight identical and independent binding sites for Mg2+ ion, which showed non-cooperativity in the binding process. The binding of Mg2+ ion was exothermic (deltaH= -17.3 kJ mol(-1)) with association binding constant of 2.08 mM(-1). The binding slightly destabilized the enzyme against thermal denaturation, as evident from absorption studies.