Catalyzes the oxidative metabolism of numerous xenobiotics, including mainly therapeutic drugs and insecticides that contain a soft nucleophile, most commonly nitrogen and sulfur and participates to their bioactivation (PubMed:9804831, PubMed:15294458, PubMed:15144220, PubMed:18948378, PubMed:18930751). Specifically catalyzes S-oxygenation of sulfur derived compounds such as thioureas-derived compounds, thioetherorganophosphates to their sulfenic acid (PubMed:9804831, PubMed:15144220). In vitro, catalyzes S-oxygenation of the second-line antitubercular drugs thiacetazone (TAZ) and ethionamide (ETA), forming a sulfinic acid and a carbodiimide via a postulated sulfenic acid intermediate (PubMed:18948378, PubMed:18930751). Also catalyzes S-oxygenation of the thioether-containing organophosphate insecticides, phorate and disulfoton (PubMed:15294458). Expressed in lung (at protein level). Expressed predominantly in lung, and at a much lesser extent in kidney. Also expressed in fetal lung, but not in liver, kidney and brain. The sequence shown is that of the allele FMO2*1. FMO2*2A is the major allele in the human population, however it encodes a truncated and catalytically inactive protein (PubMed:9804831). FMO2*2A occurs in essentially 100% of Caucasians and Asians (PubMed:9804831). FMO2*1 is present at a frequency of approximately 4% to 13% in the sample of population of African descent (PubMed:9804831, PubMed:11042094, PubMed:18794725). Belongs to the FMO family.