Carbon monoxide dehydrogenase isolation

Carbon monoxide dehydrogenase/acetyl coenzyme A synthase (CODH/ACS) describes two different classes of enzymes carbon monoxide dehydrogenase (CODH) isolated from Rhodospirillum rubrum or Carboxydothermus hydrogenoformans reversibly oxidizes CO to CO2 according to equation (2), and the bifunctional CODH/ACS enzyme from Moorella thermoacetica catalyzes the reversible reduction of CO2 to CO (CODH) and acetyl coenzyme assembly/disassembly (ACS) (equation 3). ... 

Concerning the general topic of ferredoxin and redox proteins, it is important to note the existence of several of these in various methanogens. Ferredoxin has been reported in M barkeri [iQ2], M. thermophila [249,303], and Methanococcus thermolithotrophicus [304,305]. In one case, ferredoxin is required in electron transfer from carbon monoxide dehydrogenase to a membrane-bound hydrogenase in M. thermophila [306]. Another redox protein, referred to as a glutaredoxin-like protein , has been isolated from M. thermoautotrophicum [307], but has no known function. As mentioned above, MVH gene clusters contain a sequence for a polyferredoxin of unknown function. 

Carbon monoxide dehydrogenase has been isolated from several acetogenic bacteria and purified in some cases, as shown in Table 20. This also contains details of carbon monoxide dehydrogenases from methanogens. The enzymes from C. thermoaceticum and A woodii have been compared. They both have molecular weights about 450 000 with six subunits, (0)8)3, but can exist as dimers, 0)3. The larger subunits appear to be identical in both cases, but the smaller ones differ. Nickel is present in concentrations that suggest two Ni per molecule of dimeric enzyme. There also appear to be two or three [4Fe-4S] clusters per dimeric enzyme, while the A. woodii enzyme may have a 3Fe centre. 

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