CO₂ reductase from Clostridium pasteurianum: Molybdenum dependence of synthesis and inactivation by cyanide

Purification and Properties of Reduced Ferredoxin: CO2 Oxidoreductase from Clostridium pasteurianum, a Molybdenum Iron‐Sulfur‐Protein

“…It has therefore been suggested that enzymes physiologically mediating the reduction of C02 to formate are tungsten enzymes. However, the highly purified C02 reductase from C. pasteurianum was not found to contain tungsten ( < 0.1 mol/mol molybdenum) which is in agreement with the observation that the synthesis of C 0 2 reductase in growing cultures was not affected by the addition of tungsten to the growth medium [6]. An involvement of tungsten in the catalysis of COZ reduction to formate in Clostridia is thus not obligatory.…”

“…There is no evidence on whether the molybdenum is associated with the 86000 M , or the 34000-M, subunit. The synthesis of C 0 2 reductase in growing cultures of C. pasteuriunum has recently been shown to be dependent on the presence of molybdenum in the growth medium [2,6]. It can therefore be considered to be established that C 0 2 reductase is a molybdenum enzyme.…”

“…Both the synthesis of the active reductase and the formation of formate from C02 in growing cultures were found to be dependent on molybdenum [2,6] ; furthermore the enzyme is inactivated by low concentrations of cyanide [6] as are other inolybdoenzymes. The involvement of a metal in the catalytic mechanism was also indicated by the finding that the enzyme is reversibly inhibited by low concentrations of azide (Ki = 4 pM) and by other ligands to transition metals [4].…”

Nicotinamide Adenine Dinucleotide Phosphate-Dependent Formate Dehydrogenase from Clostridium thermoaceticum: Purification and Properties

“…Likewise the inhibition by EDTA supports this view. The enzymes from C. acidiurici and C. pasteurianum are also strongly inhibited by cyanide and EDTA, indicating that these enzymes contain a metal or metals (15,30). Cyanide inhibits the molybdenum-containing xanthine oxidase and related enzymes, and it has been shown that cyanide reacts with the molybdenum (7).…”

“…In the latter organism, as with C. thermoaceticum (2), tungstate stimulates the formation of formate dehydrogenase more than molybdate does. The formation of formate dehydrogenase is also stimulated by selenium in Clostridium sticklandii and Methanococcus vannielii (28) and by molybdenum in Clostridium pasteurianum (30). These results may indicate that the electron transfer catalyzed by formate dehydrogenase is mediated by enzyme-bound metals.…”