By immobilizing catalase on a nanocomposite containing functionalized multi-walled carbon nanotubes and L-cysteine modified gold nanoparticles, a third generation biosensor was developed for determination of the hydrogen peroxide. The cyclic voltammograms of catalase on the nanocomposite modified glassy carbon electrode showed a pair of well-defined quasi-reversible redox peaks with the formal potential of -441 +/- 2 mV versus Ag/AgCl at a scan rate of 0.05 V/s. The heterogeneous electron transfer constant was calculated to be 8.72 s(-1). The enzyme electrode response toward hydrogen peroxide was linear in the concentrations ranging from 1 nM to 1 mu M, with a detection limit of 0.5 nM. The apparent Michaelis-Menten constant was calculated to be 0.34 mu M. (C) 2012 Elsevier Ltd. All rights reserved.