Entrapping of Tyrosinase in a System of Reverse Micelles

Abstract

The enzymatic activity of tyrosinase was studied both in aqueous and organic media. In the latter case tyrosinase was entrapped in a system of reverse micelles of Aerosol OT in octane. At hydration degree 25, when the inner cavity of the reverse micelles was comparable with the size of a tetrameric tyrosinase form known for aqueous solutions, an optimum level of catalytic activity was observed. Another peak of catalytic activity of tyrosinase was observed at hydration degree 12, when the size of the inner cavity of the reverse micelles was consistent with a monomeric form of tyrosinase. Thus, the system of reverse micelles can be exploited as a medium for the investigation of the monomeric form of tyrosinase, which is unstable in aqueous solution.

Oxidation Catalysis by Enzymes in Microemulsions

“…Nevertheless, the effect of water content of the microemulsion towards the initial rate of the reaction did not demonstrate a bell-shaped dependence, but showed an increase followed by a plateau. Shipovsov et al [97], in contrast to the previously reported data, found that when using isooctane and cyclohexane the profile of specific enzymatic activity (log(V max /[E])) versus w o displayed two peaks, at w o = 12 and w o = 25. Estimation of the volume of reverse micelles and correlation with the molecular volume of tyrosinase monomers and multimers provided evidence that tyrosinase is likely to exist in two different catalytically active forms when entrapped in reverse micelles, specifically, a monomeric form at w o = 12 and a tetrameric form at w o = 25.…”

Activation of laccase bioelectrocatalysis of O2 reduction to H2O by carbon nanoparticles

“…For catechol oxidation 0.1-5 nm laccase was added to a solution containing 0.5 mM catechol in 0.1 M sodium citrate-sulphate buffer, pH 5. A molar absorption coefficient of catechol e 405 = 760 M À1 cm À1 was used [32,33]. One substrate unit (U) is equivalent to the amount of laccase that catalyses the oxidation of 1 lmol of a substrate (catechol) min À1 .…”

Spraying Enzymes in Microemulsions of AOT in Nonpolar Organic Solvents for Fabrication of Enzyme Electrodes

“…w 0 ) 25 corresponds to the size of a tetrameric form of Tyr, 45 whereas w 0 ) 12 corresponds to a catalytically active monomeric form of Tyr. 43 The catalytic activity of GOx (Figure 1b) is not so much depressed by the organic solvent as in the case of Tyr, but it also increases with increasing w 0 and approaches the level characteristic of the aqueous media at w 0 g 15. Dynamic light-scattering studies 44 evidenced that the mean size of RM at w 0 ) 14-25 is optimal for entrapment of the GOx dimer molecule, ∼7 nm in diameter, 63 whereas at higher values of w 0 , RM may incorporate several GOx molecules.…”