Iron-sulfur proteins formate dehydrogenase

Formate dehydrogenases are a diverse group of enzymes found in both prokaryotes and eukaryotes, capable of converting formate to CO2. Formate dehydrogenases from anaerobic microorganisms are, in most cases, Mo- or W- containing iron-sulfur proteins and additionally flavin or hemes. Selenium cysteine is a Mo- ligand. 

Succinate dehydrogenase, like aconitase, is an iron—sulfur protein. Indeed, succinate dehydrogenase contains three different kinds of iron—sulfur clusters, 2Fe-2S (two iron atoms bonded to two inorganic sulfides), 3Fe-4S, and 4Fe-4S. Succinate dehydrogenase— which consists of two subunits, one 70 kd and the other 27 kd—differs from other enzymes in the citric acid cycle in being embedded in the inner mitochondrial membrane. In fact, succinate dehydrogenase is directly associated with the electron-transport chain, the link between the citric acid cycle and ATP formation. FADH2 produced by the... 

Trimethylamine dehydrogenase is an iron-sulfur flavoprotein found in the methylotrophic bacterium Methylophilus methylotrophus W3A1. It catalyzes the oxidative N-demethylation of trimethylamine by water with formation of dimethylamine and formaldehyde (Steenkamp and Mallinson, 1976). The protein is a symmetrical dimer consisting of 166kDa subunits (Kasprzak et al., 1983 Lim et al., 1982). Each subunit contains one 4Fe-4S center and one FMN cofactor. The latter is bound covalently through the 6... 

Although formate dehydrogenase activity is widely distributed in bacteria, only E. coli and several anaerobic organisms are known to possess the selenium-dependent form of the enzyme. These are complex enzymes that from E. coli, for example, has an MW of approximately 600,CKX) and contains 4 hemes, 4 equivalents of molybdenum, 56 of nonheme iron, 53 of acid labile sulfur, and 4 of selenium. The enzyme complex contains three types of subunits with MW of IIO.CKK), 32,000, and 20,(XK). Each of the four 110,000-Da subunits contains one equivalent of selenium which is present as selenocy-steine. More detailed analysis has focused on the incorporation of selenocysteine into this protein than into any other selenoproteins . ... 

Molybdoenzymns At present, 6 oligomeric oxi-doreductases are known, which contain Mo as an essential constituent 1. Nitrogenase (see) 2. Nitrate reductase, EC 1.6.6.3 (see) 3. Xanthine oxidase, EC 1.2.3.2 (see), from animals and bacteria 4. Aldehyde oxidase, EC 1.2.3.1 from animal liver, which catalyses the reaction R-CHO + HjO R-COOH + 2H + 2e 5. Sulfite oxidase, EC 1.18.3.1 from mammalian and bird liver (Af, 114,000 2 subunits), which catalyses the reaction S03 + HjO-> SO/ + 2H + 2e this enzyme also contains a b5-like cytochrome and passes electrons directly to cytochrome c in the respiratory chain and 6. Formate dehydrogenase, EC 1.2.1.2, a membrane-bound protein from E. coli, containing one atom each of molybdenum and selenium, one heme group and nonheme iron-sulfur centers. It is NAD -dependent and catalyses the reaction HCOO + NAD CO2 -I- NADH. 

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