TitleCharacterization of sulfoxygenation and structural implications of human flavin-containing monooxygenase isoform 2 (FMO2.1) variants S195L and N413K.
Publication TypeJournal Article
Year of Publication2009
AuthorsKrueger SK, Henderson MC, Siddens LK, VanDyke JE, Benninghoff AD, P Karplus A, Furnes B, Schlenk D, Williams DE
JournalDrug Metab Dispos
Date Published2009 Aug
KeywordsCholates, Databases, Protein, Enzyme Stability, Genotype, Hot Temperature, Humans, Hydrogen-Ion Concentration, Isoenzymes, Kinetics, Magnesium, Models, Molecular, NADP, Oxidation-Reduction, Oxygenases, Phenotype, Polymorphism, Single Nucleotide, Protein Conformation, Protein Denaturation, Recombinant Proteins, Structure-Activity Relationship, Sulfoxides

Catalytically active human flavin-containing monooxygenase isoform 2 (FMO2.1) is encoded by an allele detected only in individuals of African or Hispanic origin. Genotyping and haplotyping studies indicate that S195L and N413K occasionally occur secondary to the functional FMO2*1 allele encoding reference protein Gln472. Sulfoxygenation under a range of conditions reveals the role these alterations may play in individuals expressing active FMO2 and provides insight into FMO structure. Expressed S195L lost rather than gained activity as pH was increased or when cholate was present. The activity of S195L was mostly eliminated after heating at 45 degrees C for 5 min in the absence of NADPH, but activity was preserved if NADPH was present. By contrast, Gln472 was less sensitive to heat, a response not affected by NADPH. A major consequence of the S195L mutation was a mean 12-fold increase in K(m) for NADPH compared with Gln472. Modeling an S213L substitution, the equivalent site, in the structural model of FMO from the Methylophaga bacterium leads to disruption of interactions with NADP(+). N413K had the same pattern of activity as Gln472 in response to pH, cholate, and magnesium, but product formation was always elevated by comparison. N413K also lost more activity when heated than Gln472; however, NADPH attenuated this loss. The major effects of N413K were increases in velocity and k(cat) compared with Gln472. Although these allelic variants are expected to occur infrequently as mutations to the FMO2*1 allele, they contribute to our overall understanding of mammalian FMO structure and function.

Alternate JournalDrug Metab. Dispos.
PubMed ID19420133
PubMed Central IDPMC2712441
Grant ListP30 ES000210 / ES / NIEHS NIH HHS / United States
R01 HL038650 / HL / NHLBI NIH HHS / United States
HL038650 / HL / NHLBI NIH HHS / United States
P30-ES00210 / ES / NIEHS NIH HHS / United States