The metalloporphrins FeTPPS and MnTPPS [TPPS standing for meso- tetrkis (p-sulfonatophenyl) porphyrin], were used as the catalysts for NADH oxidation. The reaction kinetics in solution was measured by UV- vis spectroscopy. It was found that in neutral deoxygenated solution, the presence of FeTPPS or MnTPPS decreases the overpotential of NADH oxidation at a glassy carbon electrode, the processes are explained in terms of EC mechanism. In oxygen-saturated solution, MTPPS as an electron-transfer mediator accelerated NADH oxidation, and reduced MTPPS was regeneraed via chemical oxidation by O~2. The rate constant for the oxidation of NADH by FeTPPS was measured as 3.3mol^-^1.L.s^- ^1, however, for MnTPPS the rate constant was about a half of that for FeTPPS. The prospects of using MTPPS as biomimitic catalysts for NADH oxidation are discussed.

Key words: PORPHYRIN, IRON, MANGANESE, COMPLEX COMPOUNDS, KINETIC ANALYSIS, BIOCATALYSIS, COENZYME, OXIDATION