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The interaction of α‐amylase from Bacillus amyloliquefaciens with divalent cobalt ion was studied by equilibrium dialysis and isothermal titration microcalorimetry methods at 27 °C in neutral solution at pH = 7.0. A new equation with a useful graphical method, very similar to the Scatchard plot was introduced to obtain a dissociation equilibrium constant using microcalorimetric data. The constant is remarkably like that obtained from a normal Scatchard plot, which uses equilibrium dialysis data. The enzyme activity increased significantly with an increasing concentration of cobalt; however, the temperature of denaturation of the enzyme decreased.

The inhibition effect of metal ions on beta amylase activity was studied. The inhibitor-binding constant (Ki) was determined by spectrophotometric and isothermal titration calorimetric (ITC) methods. The binding of calcium, magnesium and zinc ion as inhibitors at the active site of barley beta amylase was studied at pH = 4.8 (sodium acetate 16 mM) and T = 300K. The Ki and enthalpy of binding for calcium (13.4, 13.1 mM and -14.3 kJ/mol), magnesium (18.6, 17.8mM and -17.7 kJ/mol) and zinc (17.5, 17.7 mM and -20.0 kJ/mol) were found by spectrophotometric and ITC methods respectively.