Species, organ and cellular variation in the flavin-containing monooxygenase

The distribution of the flavin-containing monooxygenase (EC1.14.13.8) (FMO) between species, organs and cell types is summarized with particular reference to the organ specific forms present in mammalian lung and liver. The role of the FMO relative to cytochrome P-450 in the oxidation of the sulfur atoms of organosulfur compounds is considered with particular reference to the hepatatoxicant thiobenzamide, the insecticide phorate and the drug, thioridazine. Of special interest is the relative role of these enzymes in complex metabolic pathways of xenobiotics.