We recently showed that by introduction of a second distal histidine (Leu29 to His29 mutation) in the heme pocket of sperm whale myoglobin (Mb), L29H Mb mutant exhibits an enhanced peroxidase activity compared to wild type (WT) Mb using H2O2 as an oxidant. In this study, we further showed that when L29H Mb was immobilized in didecyldimethylammonium bromide (DDAB) on glassy carbon electrode (GCE), it can efficiently reduce O2 in aerobic buffer solution to H2O2, followed by electrode-driven oxidation of guaiacol, a common peroxidase substrate, which is more effective (∼3.6-fold at pH = 7.0) ...