Multiple drug resistance (MDR) Tuberculosis (TB), leads to increased use of “second-line” drugs; one of the most effective is ethionamide (ETA). ETA is a prodrug metabolized by a mycobacterial flavin-containing monooxygenase (EtaA) as well human flavin-containing monooxygenases (FMOs). Of the five functional FMOs of humans, FMOs 1, 2, and 3...