Several types of redox protein films have been developed to achieve direct electron exchange of proteins or enzymes with electrodes. The direct electrochemistry of these protein or enzyme films provides a model for investigating mechanisms of redox transformations between enzyme molecules in biocatalysis and metabolic processes involving electron transportation in biological systems. Biocompatible nanosized polyamidoamine (PAMAM) dendrimer films provided a suitable microenvironment for heme proteins to transfer electron directly with underlying pyrolytic graphite (PG) electrodes.