We report the first direct electrochemistry of CYP109C1, CYP109C2 and CYP109D1 from the myxobacterium Sorangium cellulosum So ce56 immobilized on the screen-printed graphite electrode (SPE) modified by a didodecyldimethylammonium bromide (DDAB) film. Electrochemical response was investigated by cyclic voltammetry. Cyclic voltammograms in a deoxygenated argon saturated 0.1 M potassium phosphate buffer, pH 7.4, demonstrated a reversible redox process with E degrees' of -0.305 +/- 0.005 V, -0.313 +/- 0.005V, -0.309 +/- 0.005V (vs. Ag/AgCl) for CYP109C1, CYP109C2 and CYP109D1, respectively. The apparent surface coverages were (2.5 +/- 0.2) x 10 (11), (2.5 +/- 0.2) x 10 (11), (3.1 +/- 0.2) x 10 (11) mol cm (2), which corresponded to 5-6% of the total amount of protein that was consumed by the immobilization process. The rate constant K-s, of heterogeneous electron transfer between the hemoproteins and the SPE modified by DDAB film (SPE/DDAB) were determined as 0.39 +/- 0.01 s (1), 0.35 +/- 0.01 s (1), and 0.43 +/- 0.02 s (1) for CYP109C1, CYP109C2 and CYP109D1, respectively. The investigated CYPs (CYP109C1, CYP109C2 and CYP109D1) demonstrated electrocatalytic activity detected by an increase of the reduction current in the presence of dissolved oxygen. Upon addition of the substrates (myristic acid and the norisoprenoid a-ionone) in the air-saturated solution, the reduction peak current of dissolved oxygen increased, which manifested the catalytic behavior of CYP109C2 and CYP109D1 towards the substrates. CYP109D1-depended electrocatalytic hydroxylation of the myristic acid was analyzed by mass-spectrometry after electrolysis at controlled working electrode potential. (C) 2016 Elsevier Ltd. All rights reserved.