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 wellknown 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 enzymeelectrode has good characteristics: the calculated sensitivity was 40.9±0.5 mAmol−1Lcm−2 for TMA, 43.3±0.1 mA mol−1Lcm−2 for NH3, 45.2±2.2 mAmol−1Lcm−2 for TEA, and 39.3±0.6 mAmol−1Lcm−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.