Involved in the dimethyl sulfide degradation pathway. Catalyzes the oxidation of dimethylsulfone (DMSO2) to yield methanesulfinate, which is oxidized spontaneously to methanesulfonate in the presence of dioxygen and FMNH2. •

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	PMID	Title & Author	Abstract	Year
0	27392454	The reduced flavin-dependent monooxygenase SfnG converts dimethylsulfone to methanesulfinate. Wicht DK.	The biochemical pathway through which sulfur may be assimilated from dimethylsulfide (DMS) is proposed to proceed via oxidation of DMS to dimethylsulfoxide (DMSO) and subsequent conversion of DMSO to dimethylsulfone (DMSO2). Analogous chemical oxidation processes involving biogenic DMS in the atmosphere result in the deposition of DMSO2 into the terrestrial environment. Elucidating the enzymatic pathways that involve DMSO2 contribute to our understanding of the global sulfur cycle. Dimethylsulfone monooxygenase SfnG and flavin mononucleotide (FMN) reductase MsuE from the genome of the aerobic soil bacterium Pseudomonas fluorescens Pf0-1 were produced in Escherichia coli, purified, and biochemically characterized. The enzyme MsuE functions as a reduced nicotinamide adenine dinucleotide (NADH)-dependent FMN reductase with apparent steady state kinetic parameters of Km = 69 μM and kcat/Km = 9 min(-1) μM (-1) using NADH as the variable substrate, and Km = 8 μM and kcat/Km = 105 min(-1) μM (-1) using FMN as the variable substrate. The enzyme SfnG functions as a flavoprotein monooxygenase and converts DMSO2 to methanesulfinate in the presence of FMN, NADH, and MsuE, as evidenced by (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy. The results suggest that methanesulfinate is a biochemical intermediate in sulfur assimilation.	2016
1	31753487	Structure and function of the two-component flavin-dependent methanesulfinate monooxygenase within bacterial sulfur assimilation. Soule J, Gnann AD, Gonzalez R, Parker MJ, McKenna KC, Nguyen SV, Phan NT, Wicht DK, Dowling DP.	Methyl sulfur compounds are a rich source of environmental sulfur for microorganisms, but their use requires redox systems. The bacterial sfn and msu operons contain two-component flavin-dependent monooxygenases for dimethylsulfone (DMSO2) assimilation: SfnG converts DMSO2 to methanesulfinate (MSI-), and MsuD converts methanesulfonate (MS-) to sulfite. However, the enzymatic oxidation of MSI- to MS- has not been demonstrated, and the function of the last enzyme of the msu operon (MsuC) is unresolved. We employed crystallographic and biochemical studies to identify the function of MsuC from Pseudomonas fluorescens. The crystal structure of MsuC adopts the acyl-CoA dehydrogenase fold with putative binding sites for flavin and MSI-, and functional assays of MsuC in the presence of its oxidoreductase MsuE, FMN, and NADH confirm the enzymatic generation of MS-. These studies reveal that MsuC converts MSI- to MS- in sulfite biosynthesis from DMSO2.	2020
2	12835925	Characterization and identification of genes essential for dimethyl sulfide utilization in Pseudomonas putida strain DS1. Endoh T, Kasuga K, Horinouchi M, Yoshida T, Habe H, Nojiri H, Omori T.	Microbial dimethyl sulfide (DMS) conversion is thought to be involved in the global sulfur cycle. We isolated Pseudomonas putida strain DS1 from soil as a bacterium utilizing DMS as a sole sulfur source, and tried to elucidate the DMS conversion mechanism of strain DS1 at biochemical and genetic level. Strain DS1 oxidized DMS to dimethyl sulfone (DMSO(2)) via dimethyl sulfoxide, whereas the oxidation was repressed in the presence of sulfate, suggesting that a sulfate starvation response is involved in DMS utilization by strain DS1. Two of the five DMS-utilization-defective mutants isolated by transposon 5 (Tn 5) mutagenesis had a Tn 5 insertion in the ssuEADCBF operon, which has been reported to encode a two-component monooxygenase system (SsuED), an ABC-type transporter (SsuABC), and a small protein (SsuF), and also to play a key role in utilization of sulfonates and sulfate esters in another bacterium, P. putida strain S-313. Disruption of ssuD and SsuD enzymatic activity demonstrated that methanesulfonate is a metabolic intermediate of DMS and desulfonated by SsuD. Disruption of ssuC or ssuF also led to a DMS-utilization-defective phenotype. Another two mutants had a defect in a gene homologous to pa2354 from P. aeruginosa PAO1, which encodes a putative transcriptional regulator, while the remaining mutant had a defect in cysM encoding O-acetylserine (thiol)-lyase B.	2003
3	15661012	The sigma54-dependent transcriptional activator SfnR regulates the expression of the Pseudomonas putida sfnFG operon responsible for dimethyl sulphone utilization. Endoh T, Habe H, Nojiri H, Yamane H, Omori T.	Pseudomonas putida DS1 is able to utilize dimethyl sulphide through dimethyl sulphoxide, dimethyl sulphone (DMSO2), methanesulphonate (MSA) and sulphite as a sulphur source. We previously demonstrated that sfnR encoding a sigma54-dependent transcriptional regulator is essential for DMSO2 utilization by P. putida DS1. To identify the target genes of SfnR, we carried out transposon mutagenesis on an sfnR disruptant (DMSO2-utilization-defective phenotype) using mini-Tn5, which contains two outward-facing constitutively active promoters; as a result, we obtained a mutant that restored the ability to utilize DMSO2. The DMSO2-positive mutant carried a mini-Tn5 insertion in the intergenic region between two opposite-facing operons, sfnAB and sfnFG. Both sfnA and sfnB products were similar to acyl-CoA dehydrogenase family proteins, whereas sfnF and sfnG encoded a putative NADH-dependent FMN reductase (SfnF) and an FMNH2-dependent monooxygenase (SfnG). Disruption and complementation of the sfn genes indicated that the sfnG product is essential for DMSO2 utilization by P. putida DS1. Furthermore, an enzyme assay demonstrated that SfnG is an FMNH2-dependent DMSO2 monooxygenase that converts DMSO2 to MSA. It was revealed that the expression of the sfnFG operon is directly activated by the binding of SfnR at its upstream region. Site-directed mutagenesis of the SfnR binding sequences allowed us to define a potential recognition sequence for SfnR. These results provided insight into regulation of sulphate starvation-induced genes in bacteria.	2005

Endoh T , Habe H , Nojiri H , et al. The σ54-dependent transcriptional activator SfnR regulates the expression of the Pseudomonas putida sfnFG operon responsible for dimethyl sulphone utilization[J]. Molecular Microbiology, 2005, 55(3):897-911. Endoh T , Kasuga K , Horinouchi M , et al. Characterization and identification of genes essential for dimethyl sulfide utilization inPseudomonas putidastrain DS1[J]. Applied Microbiology & Biotechnology, 2003, 62(1):83-91.