Molecular Cloning, Sequence, and Expression of Mouse Flavin-Containing Monooxygenases 1 and 5 (FMO1 and FMO5)

Full-length cDNA clones encoding FMO1 and FMO5 have been isolated from a library constructed with mRNA from the liver of a female CD-1 mouse. The derived sequence of FMO1 contains 2310 bases: 1596 in the coding region, 301 in the 5′-flanking region, and 413 in the 3′-flanking region. The sequence for FMO5 consists of 3168 bases; 1599 in the coding region, 812 in the 5′-flanking region, and 757 in the 3′-flanking region. The sequence of FMO1 encodes a protein of 532 amino acids with a predicted molecular weight of 59.9 kDa and shows 83.3% identity to human FMO1 and 83-94% identity to other FMO1 homologs. FMO5 encodes a protein of 533 amino acids with a predicted molecular weight of 60.0 kDa and 84.1% identity to human FMO5 and 83-84% identity to other FMO5 orthologs. Two GxGxxG putative pyrophosphate binding domains exist beginning at positions 9 and 191 for FMO1, and 10 and 192 for FMO5. Mouse FMO1 and FMO5 were expressed in E. coli and show similar mobility to the native proteins as determined by SDS-PAGE. The expressed FMO1 protein showed activity toward methimazole, and FMO5 was active toward n-octylamine. In addition, FMO1 was shown to metabolize radiolabeled phorate, whereas FMO5 showed no activity toward phorate.