Effect of ionic and non-ionic surfactants on the activity and stability of mushroom tyrosinase

Three typical surfactants were selected based on their head group charges: an anionic surfactant sodium di-2-ethylhexylsulfosuccinate (AOT), a non-ionic surfactant polyethylene glycol hexadecyl ether (Brij 52), and a cationic surfactant cetyltrimethylammonium bromide (CTAB). The kinetic parameters (such as K-m V-max, X, optimal pH and temperature, and activation energy) and the thermostability of the enzyme at different temperatures (including half-lives, deactivation constants, and activation energies for enzyme deactivation) were determined and compared in the absence and presence of the three surfactants. Both AOT and Brij 52 showed the ability of activating the enzyme while CTAB inactivated it. In terms of stability, Brij 52-induced stabilization and AOT and CTAB-mediated destabilization of the enzyme were observed. Thermoinactivation for both the native and surfactant-treated tyrosinases generally obeyed the classical first-order kinetics. The effects of the three surfactants may be related to a conformational change on the enzyme. (c) 2007 Elsevier B.V. All rights reserved.