The influence of composition and structure of water-in-oil microemulsions on activities of Iraqi Turnip peroxidase

The activity of the enzyme Iraqi Turnip peroxidase (ITP) is studied in a reverse microemulsion composed of chloroform, aqueous buffer, sodium dodecylsulfate (SDS) and alcohols of the homologous series 1-propanol to 1-hexanol through the measurements of absorbancy of the product of oxidation at the wavelength of 470 nm in the course of reactions. The ITP catalyzed reaction is the oxidation of guaiacol by hydrogen peroxide. Maximum enzyme activity was obtained at ω0 (molar ratio of water to surfactant) = 8. It was found that the oxidation reaction obeyed Michaelis–Menten kinetics in the investigated concentration rang (0.08–0.8 mM) of the substrate, and the Michaelis constant Km and maximal reaction rate Vm were determined. The enzyme inhibition caused by the alcohols in microemulsions is a consequence of both the solubility of the alcohols in the buffer and the flexibility of the interfacial film.