Abstract

In the present study, we reported for the first time the effect of various concentrations (0.5– 3.0 mM) of Mg²⁺ and Al³⁺ ions on the kinetics and thermodynamics of Aspergillus niger invertases for sucrose hydrolysis. We found that both metal ions enhanced the affinity of invertase for sucrose by decreasing the K_m. In the presence of 0.5 mM Al³⁺ ions invertase have maximum affinity for sucrose (K_m = 0.00914 M sucrose). Invertase was activated by Mg²⁺ ions at low concentrations (0.5–2.0 mM) and 341% increase in turnover (K_cat) and maximum decrease in ΔG* was observed in the presence of 0.5 mM Mg²⁺ ions. The entropy change for activation of substrate hydrolysis (ΔS*) was increased by all concentrations of Mg²⁺ ions and was highest (-94 J mol^-1 K^-1) for invertases bound with 1.5 mM Mg²⁺ ions.

Keywords: Aspergillus niger, invertase, Mg²⁺ ions, Al³⁺ ions, kinetics, physiochemical characterization, thermodynamics.

Graphical Abstract