Reductase DMSO reductase

The [2Fe 2S], [3Fe S], and [4Fe S] clusters that are found in simple Fe S proteins are also constituents of respiratory and photosynthetic electron transport chains. Multicluster Fe S enzymes such as hydrogenase, formate dehydrogenase, NADH dehydrogenase, and succinate dehydrogenase feed electrons into respiratory chains, while others such as nitrate reductase, fhmarate reductase, DMSO reductase, and HDR catalyze the terminal step in anaerobic electron transport chains that utihze nitrate, fumarate, DMSO, and the CoB S S CoM heterodisulfide as the respiratory oxidant. All comprise membrane anchor polypeptide(s) and soluble subunits on the membrane surface that mediate electron transfer to or from Mo cofactor (Moco), NiFe, Fe-S cluster or flavin active sites. Multiple Fe-S clusters define electron transport pathways between the active site and the electron donor or... 

Sulfite Oxidase Nitrate Reductase DMSO Reductase... 

The enzymes that utilize molybdenum can be grouped into two broad categories (1) the nitrogenases, where Mo is part of a multinu-clear metal center, or (2) the mononuclear molybdenum enzymes, such as xanthine oxidase (XO), dimethyl sulfoxide (DMSO) reductase, formate dehydrogenase (FDH), and sulfite oxidase (SO). The last... 

The three known crystal structures of molybdopterin-containing enzymes are from members of the first two families the aldehyde oxido-reductase from D. gigas (MOP) belongs to the xanthine oxidase family (199, 200), whereas the DMSO reductases from Rhodobacter (R.) cap-sulatus (201) and from/ , sphaeroides (202) and the formate dehydrogenase from E. coli (203) are all members of the second family of enzymes. There is a preliminary report of the X-ray structure for enzymes of the sulfite oxidase family (204). 

The conditions under which these function and their regulation depend on the organism. For example, in Escherichia coli, oxygen represses the synthesis of the other reductases, and under anaerobic conditions the reductases for fumarate, DMSO, and TMAO are repressed by nitrate. This does not apply to Wolinella succinogenes in which sulfur represses the synthesis of the more positive electron acceptors nitrate and fumarate (Lorenzen et al. 1993). The DMSO reductase from Escherichia coli (Weiner et al. 1988) has a broad substrate versatility, and is able to reduce a range of sulfoxides and A-oxides. Anaerobic sulfate reduction is not discussed here in detail. 

McEwan AG, IP Ridge, CA McDevitt, P Hugenholtz (2002) The DMSO reductase family of microbial molybdenum enzymes molecular properties and the role in the dissimilatory reduction of toxic elements. 

III. DMSO-reductase family (bacterial DMSO reductase DMSO to DMS... 

The pH-dependence is of particular relevance for groups that occur in three subsequent oxidation states because the two reduction potentials j° and E° in Equation 13.14 in general have different pH dependence. For example, the paramagnetic Wv state of the tungsto-enzyme DMSO reductase affords an EPR signal with a maximal spin count of 40% of protein concentration at pH = 5 when E° - E° +10 mV, whereas at pH = 8 no signal is detected at all because E° E° (Hagedoorn et al. 2003). 

Hagedoorn, P.-L., Hagen, W.R., Stewart, L.J., Docrat, A., Bailey, S., and Garner, C.D. 2003. Redox characteristics of the tungsten DMSO reductase of Rhodobacter capsulatus. FEBS Letters 555 606-610. 

Fe 2S], a [4Fe-4S] and a [3Fe-4S] center. The enzyme catalyzes the reversible redox conversion of succinate to fumarate. Voltammetry of the enzyme on PGE electrodes in the presence of fumarate shows a catalytic wave for the reduction of fumarate to succinate (much more current than could be accounted for by the stoichiometric reduction of the protein active sites). Typical catalytic waves have a sigmoidal shape at a rotating disk electrode, but in the case of succinate dehydrogenase the catalytic wave shows a definite peak. This window of optimal potential for electrocatalysis seems to be a consequence of having multiple redox sites within the enzyme. Similar results were obtained with DMSO reductase, which contains a Mo-bis(pterin) active site and four [4Fe 4S] centers. 

Figure 17.2 The structure of the pterin cofactor (1) which is common to most molybdenum- and tungsten-containing enzymes and schematic active site structures for members of the xanthine oxidase (2,3), sulfite oxidase (4) and DMSO reductase (5-7) enzyme families. (From Enemark et al., 2004. Copyright (2004) American Chemical Society.)...

In the case of the DMSO reductase family, as pointed out above, the metal centre is bound to two molecules of the cofactor. DMSO reductase itself catalyses the reduction of dimethylsulfoxide to dimethylsulfide with incorporation of the oxygen atom of DMSO into water. The active site of the oxidized enzyme is an L2MoVI0(0-Ser) centre, which, upon reduction, loses the M=0 ligand to give a L2MoIV(0-Ser) centre. In the catalytic... 

In this section, calculations of the MCD spectra of the Mo-containing proteins, sulfite oxidase (167), and dimethyl sulfoxide (DMSO) reductase, (168) will be discussed. These two... 

The reduction of DMSO catalyzed by molybdenum is an important step in the process of anaerobic respiration carried out by a number of bacteria (169). Much like sulfite oxidase, early MCD studies of DMSO reductase were complicated by the presence of heme iron (173). The discovery of two enzymes that do not include an iron center led to the measurement of MCD spectra of Rhodobacter sphaeroides DMSO reductase that could be assigned exclusively in terms of transitions of the Mo site (Fig. 10b) (174). The six major peaks are assigned as LMCT transitions from the three highest energy occupied orbitals to the two lowest unoccupied orbitals (174). 

Fig. 10. (a) Model of DMSO reductase Mo active site, (b) Simulated (168) and experimental (174) MCD spectra of DMSO reductase. 

DMSO reductase reduces dimethylsulfoxide to dimethylsulfide (Eq. 16-62) as part of the biological sulfur cycle.647 648d... 

A number of other reductases and dehydrogenases, including dissimilatory nitrate reductases of E. coli and of denitrifying bacteria (Chapter 18), belong to the DMSO reductase family. Other members are reductases for biotin S-oxide,649 trimethylamine N-oxide, and polysulfides as well as formate dehydrogenases (Eq. 16-63), formylmethanofuran dehydrogenase (Fig. 15-22,... 

The active site structures of the three classes of molybdenum-containing enzymes are compared in Fig. 16-32. In the DMSO reductase family there are two identical molybdopterin dinucleotide coenzymes complexed with one molybdenum. However, only one of these appears to be functionally linked to the Fe2S2 center. 

Disulfide bridges (crosslinkages) 65, 80 cleavage of 115-116 cleavage with performic acid 115 locating 119 in proteins 80 reduction of 115, 785 Dithioerythritol 115 Dithionite ion 779 Dithiothreitol 98,115, 822 Dityrosine linkages 81 DMSO reductase 890 DNA... 

From an analysis of their protein sequences, dmso reductase, respiratory nitrate reductase, and formate dehydrogenase (FDH) are assigned as members of a large... 

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