The enzyme from Escherichia coli catalyses the desulfonation of a wide range of aliphatic sulfonates (unsubstituted C1- to C14-sulfonates as well as substituted C2-sulfonates). Does not desulfonate taurine (2-aminoethanesulfonate) or aromatic sulfonates. Does not use FMN as a bound cofactor. Instead, it uses reduced FMN (i.e., FMNH2) as a substrate. FMNH2 is provided by SsuE, the associated FMN reductase (EC 1.5.1.38).
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SYSTEMATIC NAME
IUBMB Comments
alkanesulfonate,FMNH2:oxygen oxidoreductase
The enzyme from Escherichia coli catalyses the desulfonation of a wide range of aliphatic sulfonates (unsubstituted C1- to C14-sulfonates as well as substituted C2-sulfonates). Does not desulfonate taurine (2-aminoethanesulfonate) or aromatic sulfonates. Does not use FMN as a bound cofactor. Instead, it uses reduced FMN (i.e., FMNH2) as a substrate. FMNH2 is provided by SsuE, the associated FMN reductase (EC 1.5.1.38).
the two-component alkanesulfonate monooxygenase system, with the flavin mononucleotide reductase, SsuE, being a part of it besides SsuD, utilizes reduced flavin as a substrate to catalyze a unique desulfonation reaction during times of sulfur starvation, protein-protein interactions are important in the mechanism of flavin transfer
mechanism of flavin reduction in the alkanesulfonate monooxygenase system, the FMN reductase, SsuE, catalyzes the reduction of FMN by NADPH, and the reduced flavin is transferred to the monooxygenase, SsuD, overview
no substrates are taurine, methanesulfonic acid, benzenesulfonic acid, L-cysteic acid, ethanedisulfonic acid, toluene-4-sulfonic acid, p-sulfobenzoic acid, benzenesulfonic acid, 4-hydroxybenzenesulfonic acid, SsuD is able to desulfonate C-2 to C-10 unsubstituted alkanesulfonates, substituted ethanesulfonic acids and HEPES, the catalytic efficiency increases with increasing chain length up to decanesulfonic acid
mechanism of flavin reduction in the alkanesulfonate monooxygenase system, consisting of the alkanesulfonate monooxygenase and the flavin mononucleotide reductase, which catalyzes the reduction of FMN by NADPH, overview
the enzyme interacts with the flavin mononucleotide reductase, SsuE, in a 1:1 monomeric association, mechanism of protein-protein interaction not leading to overall conformational changes in protein structure, overview
the two-component alkanesulfonate monooxygenase system from Escherichia coli includes an FMN reductase, SsuE, and an FMNH2-dependent alkanesulfonate monooxygenase, SsuD, involved in the acquisition of sulfur from alkanesulfonates during sulfur starvation, overview
Cys54 in SsuD may be either directly or indirectly involved in stabilizing the C4a-(hydro)peroxyflavin intermediate formed during catalysis through hydrogen bonding interactions
residues Arg226 donates a proton to the FMN-O? intermediate, triggering a conformational change that opens the enzyme to solvation and promotes product release, solvent and kinetic isotope studies
the two-component alkanesulfonate monooxygenase system from Escherichia coli includes an FMN reductase, SsuE, and an FMNH2-dependent alkanesulfonate monooxygenase, SsuD, involved in the acquisition of sulfur from alkanesulfonates during sulfur starvation, overview
the two-component alkanesulfonate monooxygenase system, with the flavin mononucleotide reductase, SsuE, being a part of it besides SsuD, utilizes reduced flavin as a substrate to catalyze a unique desulfonation reaction during times of sulfur starvation, protein-protein interactions are important in the mechanism of flavin transfer
optimal transfer of reduced flavin from NADPH-dependent FMN reductase SsuE to SsuD requires defined protein-protein interactions, but diffusion can occur under specified conditions. A SsuD variant containing substitutions of charged residues shows a 4fold decrease in coupled assays that include SsuE to provide reduced FMN, but there is no activity observed with an SsuD variant containing a deletion of the alpha-helix containing conserved charged amino acids
salt bridges between Arg297 and Glu20 or Asp111 are not critical to the desulfonation mechanism. The predicted role of residue Arg297 is to favorably interact with the phosphate group of the reduced flavin. Arg226 functions as a protection group shielding FMNOO- from bulk solvent and is more pronounced when both FMNOO- and octanesulfonate are bound
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
molecular dynamics simulations for Ssud in substrate-free form, bound with FMNH2, bound with a C4a-peroxyflavin intermediate (FMNOO?), bound with octanesulfonate, cobound with FMNH2 and octanesulfonate, and cobound with FMNOO? and octanesulfonate
has little effect on FMN or FMNH2 binding, kcat/Km value increases 3fold relative to wild-type. Is able to generate the C4a-(hydro)peroxyflavin, but the rate of formation is increased 10fold relative to wild-type
gene ssuD, the alkanesulfonate monooxygenase system, expressed from the ssuEADCB operon, is comprised of a flavin reductase encoded by ssuE and monooxygenase encoded by ssuD, ssuD expressionin strain BL21(DE3)
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