Electro-catalysis by immobilised human flavin-containing monooxygenase isoform 3 (hFMO3)

Human flavin-containing monooxygenases are the second most important class of drug-metabolizing enzymes after cytochromes P450. Here we report a simple but functional and stable enzyme-electrode system based on a glassy carbon (GC) electrode with human flavin-containing monooxygenase isoform 3 (hFMO3) entrapped in a gel cross-linked with bovine serum albumin (BSA) by glutaraldehyde. The enzymatic electrochemical responsiveness is characterised by using well-known substrates: trimethylamine (TMA), ammonia (NH3), triethylamine (TEA), and benzydamine (BZD). The apparent Michaelis-Menten constant (K'(M)) and apparent maximum current (I'(max)) are calculated by fitting the current signal to the Michaelis-Menten equation for each substrate. The enzyme-electrode has good characteristics: the calculated sensitivity was 40.9 +/- 0.5 mA mol(-1) Lcm(-2) for TMA, 43.3 +/- 0.1 mA mol(-1) Lcm(-2) for NH3, 45.2 +/- 2.2 mA mol(-1) Lcm(-2) for TEA, and 39.3 +/- 0.6 mA mol(-1) Lcm(-2) for BZD. The stability was constant for 3 days and the inter-electrode reproducibility was 12.5%. This is a novel electrochemical tool that can be used to investigate new potential drugs against the catalytic activity of hFMO3.