Flavin-containing monooxygenase (FMO, EC1.14.13.8) comprises a family of xenobiotic-metabolizing enzymes that catalyze the oxygenation of a wide variety of xenobiotics, most commonly nitrogen and sulfur. Mammals express five different FMOs in a species- and tissue- specific manner. FMO2, is expressed predominantly in lung and differs from other FMOs in that it can catalyze the N-oxygenation of certain primary alkylamines. From its initial discovery as an unique form of FMO in lung, FMO2 has been studied primarily using a rabbit animal model. The initial goal of this research was to characterize this protein in a primate animal model. To understand FMO2 protein structure at the molecular level, we first cloned cDNA from a monkey lung cDNA library. Monkey FMO2 is expressed predominantly in lung. The high expression levels and broad substrate specificity in monkey, suggests that FMO2 plays a role in xenobiotic metabolism in this primate model. We then established a heterologous expression system to generate FMO2 with biological functionality in vitro. FMO2 from baculovirus-mediated expression resembled monkey and rabbit microsomal FMO2 immunochemically and catalytically. The successful FMO2 expression in the baculovirus system will serve as a valid tool for structure studies of protein functional domains, as well as, the amino acids responsible for enzyme properties of chimeras. Human FMO2 encodes a truncated protein containing 471 amino acid residues, 64 amino acids shorter in its C-terminal than orthologs in other species. We characterized human FMO2 in terms of gene polymorphism (genotyped by Dr. Hines), protein levels and catalytic activity with human lung microsomes. An ethnically related polymorphism was observed, in which all Caucasians genotyped to date are homozygous for a truncated, enzymatically inactive enzyme which may not even be translated. Approximately 15% of humans of African descent are heterozygous for full-length FMO2, but the level of expression may not be sufficient to significantly effect drug metabolism in the lung. The results of truncated FMO2 produced from baculovirus expression suggest that the C-terminal of FMO2 might be responsible for enzyme stability and/or proper structure necessary to exert fully enzyme activity. We conclude that the human FMO2 possesses unique features compared to all other mammals examined to date including other primates. / Graduation date: 1999

Graduation date: 2001

Graduation date: 1998

Graduation date: 1996

Graduation date: 1995

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Microbiology and Molecular Genetics." Includes bibliographical references (p. 151-161).

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The mammalian FMO represents a multigene family which oxygenates a large number of xenobiotics. No physiological role has been determined for FMO, although synthesis of disulfide bonds and detoxification of dietary chemicals have been suggested. Five FMO gene subfamilies, each containing a single gene, have been identified. In this study, we determined the patterns of fetal and neonatal development of FMO1 and FMO2 in rabbit liver and lung. The expression of two major isoforms, FMO1 and FMO2, in fetal and neonatal animals were characterized at the steady state levels of mRNA. Northern and slot blot analyses were performed with cDNA probes for each isoform to provide a qualitative and quantitative profile. In order to relate developmental changes in FMO to the metabolism of xenobiotics for which lung is a target organ, the developmental expression of lung FMO (FMO2) mRNA is compared to rabbit CYP2B4 and CYP4B1 which are the major constitutive P450s in lung. The results show that the expression of FMO1 and FMO2 is tissue-dependent, although the mechanisms controlling the mRNA expression, such as rate of transcription, processing of primary RNA, efficiencies of nucleocytoplasmic transport and stability of RNA in the cytoplasm, are still unknown. The results indicate that the early development- and tissue-specific expression patterns of mRNA for FMO1 and FMO2 might play a significant role in the target organ toxicity of xenobiotics in the rabbit fetus and neonate. / Graduation date: 1995 / Best scan available. Original is a black and white photocopy.

Dissertation (Ph.D.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (p.158-180).