Effect of immobilization on kinetic and thermodynamic characteristics of sulfide oxidase from Arthrobacter species

In order to determine the impact of immobilization on biocatalytic efficacy of sulfide oxidase, the kinetic and thermodynamic properties of native and DEAE-cellulose immobilized sulfide oxidase from Arthrobacter species FR-3 were evaluated. Immobilization increased the catalytic efficiency of sulfide oxidase by producing a lower Michaelis-Menten constant (Km) and a higher rate of catalysis (Vmax) at different temperatures. The first-order kinetic analysis of thermal denaturation demonstrated that the values of enthalpy (delta H*d) and entropy (delta S*d) of immobilized sulfide oxidase were lower than the native enzyme, confirming the thermal stabilization of sulfide oxidase by immobilization. The delta H*d and delta S*d of the immobilized enzyme at 35 degrees C were 138.07 kJ/mol and 122.04 J/K/mol, respectively. These results suggest that immobilization made the sulfide oxidase from Arthrobacter sp. FR-3 thermodynamically more efficient for catalysis of sulfide oxidation.