Recently, much attention has been paid to the study of biocatalysts. It is connected with the possibility of their use under mild conditions: рН~7; Т=(293 +\- 5) К. In addition, they have a unique specificity.  We investigated carboxylase applied on carbon carriers: coals - AG-2, CAD, BAU, nanotubes. The study was carried out in a conventional electrochemical cell at the Sistem-5000 potentiostat which simultaneously measured the kinetics of decomposition of H2O2 and monitored the potential. The catalyst charge was constant 50 mg in all the experiments.  As it is known, the decomposition of Н2О2 can occur by an ionic or radical mechanism [1]. The results obtained showed that decomposition of Н2О2 can not occur on the researched catalysts (carboxylase-carbon carrier) by ionic mechanism, since in this case the initial stage would be one of the following reactions:  К [H2O] адс. + Н2О2 → К [ Н3О+]адс.+ [НО2- ] ;  НО2- + Н2О2 → H2O + О2+ ОН- ;  К [ Н3О+]адс+ ОН- → К [H2O] адс + H2O ;  Н2О2+ ОН- → H2O + НО2- ;  Since the heats of formation of Н2О and Н3О+ are the same [2], an activation energy of ~ 28.6 kJ/mol is needed for the course of this reaction. It differs significantly from the value of the activation energy of Н2О2 catalytic decomposition on the researched catalysts. Therefore, radical mechanism of Н2О2 decomposition should be applied.