Direct electrochemistry and electrocatalysis of catalase (Cat) was studied based on a nano-composite film consisting of amine functionalized graphene and gold nanoparticles (AuNPs) modified glassy carbon electrode. Graphene was synthesized chemically by Hummers and Offeman method and then was functionalized with amino groups via chemical modification of carboxyl groups introduced on the graphene surface. The nano-composite film showed an obvious promotion of the direct electron transfer between Cat and the underlying electrode, which attributed to the synergistic effect of graphene-NH2 and AuNPs. The resultant bioelectrode retained its biocatalytic activity and offered fast and sensitive H2O2 quantification. Under the optimized experimental conditions, hydrogen peroxide was detected in the concentration range from 0.3 to 600 mu M with a detection limit of 50 nM at S/N = 3. The biosensor exhibited some advantages, such as short time respond (2 s), high sensitivity (13.4 mu A/mM) and good reproducibility (RSD = 5.8%). (C) 2011 Elsevier Ltd. All rights reserved.