The Flavin-Containing Monooxygenase (FMO) is arguably the most important understudied mammalian enzyme known today. FMO is a major component of the defenses that protect humans against potentially toxic chemicals in their environment, including xenobiotics, drugs and pesticides. A compound containing a tertiary amine or a nucleophilic sulfur nucleus is efficiently N- or S-oxygenated by FMO and converted to a form more readily excreted. Even though FMO is present in high levels in every secretory cell thus far examined, a physiological basis for its action remains unclear. Knowledge of the amino acid sequence of FMO deduced from cDNA sequencing will enable an understanding of: (1) tissue or species selective FMO drug or xenobiotic metabolism, and (2) tissue specific enzyme mechanism. We have cloned human liver and human placenta FMO employing a lambda gtll antibody screening procedure. The data strongly suggest that at least for placenta FMO we have a full length cDNA. In order to confirm this we obtained FMO amino acid sequence, deduced nucleotide sequence, constructed a probe and demonstrated that this probe selectively hybridizes to FMO cDNA. In this research proposal we will accomplish the following: (1) clone human liver and placenta and hog liver FMO cDNA using a lambda gtlO oligonucleotide selection procedure. This will provide a set of cDNA in which to confirm our original clones, (2) confirm the identity of FMO cDNA clones with (a) hybridization selection, and (b) antibody fingerprinting, (3) Verify the FMO cDNA by comparing nucleotide sequence with amino acid sequence deduced from (a) gas phase peptide sequencing and (b) mass spectrometry. (4) Express the human liver and placenta FMO cDNA. These studies will provide detailed information which will explain isozyme or tissue specific FMO drug and xenobiotic metabolism. The information gained will be of therapeutic value in achieving an understanding of tissue selective targeting of drugs or drug metabolites.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM036426-03
Application #
3290384
Study Section
Physical Biochemistry Study Section (PB)
Project Start
1988-09-19
Project End
1991-08-31
Budget Start
1990-09-01
Budget End
1991-08-31
Support Year
3
Fiscal Year
1990
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Type
Schools of Pharmacy
DUNS #
073133571
City
San Francisco
State
CA
Country
United States
Zip Code
94143
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Cashman, J R (2000) Human flavin-containing monooxygenase: substrate specificity and role in drug metabolism. Curr Drug Metab 1:181-91
Cashman, J R; Xiong, Y N; Xu, L et al. (1999) N-oxygenation of amphetamine and methamphetamine by the human flavin-containing monooxygenase (form 3): role in bioactivation and detoxication. J Pharmacol Exp Ther 288:1251-60
Cashman, J R (1998) Stereoselectivity in S- and N-oxygenation by the mammalian flavin-containing and cytochrome P-450 monooxygenases. Drug Metab Rev 30:675-707
Korsmeyer, K K; Guan, S; Yang, Z C et al. (1998) N-Glycosylation of pig flavin-containing monooxygenase form 1: determination of the site of protein modification by mass spectrometry. Chem Res Toxicol 11:1145-53
Treacy, E P; Akerman, B R; Chow, L M et al. (1998) Mutations of the flavin-containing monooxygenase gene (FMO3) cause trimethylaminuria, a defect in detoxication. Hum Mol Genet 7:839-45
Cashman, J R (1997) Biocatalysts in detoxication of drugs of abuse. NIDA Res Monogr 173:225-58

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