Self-assembled monolayers of cysteine (CYST) have been constructed on polycrystalline gold (polyAu) electrode at different immersion times (timmer) in order to characterize them by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Oxidative desorption experiments allowed the calculation of the surface coverage, whereas reductive desorption informed about the binding of CYST to different gold domains. Desorption products showed different diffusion ability. The maximum coverage was already achieved at short timmer, although progressive reordering of CYST molecules led to a relevant decrease of the defects at long time, as ascertained by EIS. Functionalization of polyAu-CYST electrodes with the enzyme microperoxidase MP-11 performed by following two different binding methods showed that the enzymatically catalyzed reduction of H2O2 is enhanced when the -COOH residues of the MP-11 undecapeptide chain are firstly activated and then linked to the -NH2 functional groups of the non-activated CYST layer formed on the polyAu surface.