The direct electrochemical and electrocatalytic properties of catalase (CAT) immobilized on the multi-wall carbon nanotubes (MWCNT) modified glassy carbon (MWCNT/GC) electrode was investigated in 0.1 M Tris-HCl buffer solution. It was found that CAT immobilized on the MWCNT/GC electrode could undergo a direct and quasi-reversible reaction with the formal potential (Eo') of -0.456 V. The electrochemical reaction involves the transfer of one electron and one proton. Furthermore, La3+ can affect the electrochemical behavior of the immobilized CAT depending on the concentration of La3+. The low concentration of La3+ can promote, but the high concentration of La3+ would inhibit the electrochemical reaction of the immobilized CAT. This is due to that the different concentrations of La3+ could increase or decrease the exposure extent of the heme group in CAT. CAT immobilized on the MWCNT/GC electrode could keep its biocatalytic activity for the H2O2 reduction. These results illustrated that MWCNT is a good carrier for immobilizing the biomicromolecules. This may be useful in the biosensors and biofuel cells. (c) 2007 Elsevier B.V. All rights reserved.