Microperoxidase-11/NH2-FSM16 as a H2O2-resistant heterogeneous nanobiocatalyst: a suicide-inactivation study

The catalytic activity of heme peptides is an area of intense investigation. They are utilized for exploring the fine details of structural and functional properties of an active site, and to create minimized and industrial catalysts. The peroxidase activity and kinetics of suicide-inactivation of microperoxidase-11/FSM16 as a heterogeneous nanobiocatalyst in oxidation reaction of guaiacol were studied in the presence of high concentration of hydrogen peroxide (2 mM), as its natural suicide-substrate. The substrate concentration was first-order in relation to aromatic substrate (AH), and the ratio of suicide-substrate (H2O2) was kept much higher than the benign substrate (guaiacol). The results of kinetic analysis confirmed a similar mechanism for suicide-peroxide inactivation of horseradish peroxidase (HRP), microperoxidase (MP-11) and MP-11/NH2-FSM16. Inactivation kinetic parameters, including intact activity of MP-11/NH2-FSM16, alpha(i), and the apparent inactivation rate constant (k (i)) were obtained as 0.229 +/- A 0.009 min(-1) and 0.651 +/- A 0.041 min(-1) at [H2O2] = 2.0 mM, respectively, in 5.0 mM phosphate buffer solution (PBS; pH 7.0) at 27 A degrees C. Our results indicated that covalent immobilization of microperoxidase onto NH2-FSM16 protected the heme group against peroxide inactivation resulting in generation of an efficient peroxide-resistant heterogeneous nanobiocatalyst.