title: Fumarate reductase of Clostridium formicoaceticum. A peripheral membrane protein.
abstract: When Clostridium formicoaceticum was grown on fumarate or L-malate crude cell extracts contained a high fumarate reductase activity. Using reduced methyl viologen as electron donor the specific activity amounted to 2-3.5 U per mg of protein. Reduced benzyl viologen, FMNH2 and NADH could also serve as electron donors but the specific activities were much lower. The NADH-dependent activity was strictly membrane-bound and rather labile. Its specific activity did not exceed 0.08 U per mg of particle protein. Fumarate reductase activity was also found in cells of C. formicoaceticum grown on fructose, gluconate, glutamate and some other substrates. The methyl viologen-dependent fumarate reductase activity could almost completely be measured with intact cells whereas only about 25% of the cytoplasmic acetate kinase activity was detected with cell suspensions. The preparation of spheroplasts from cells of C. formicoaceticum in 20 mM HEPES-KOH buffer containing 0.6 M sucrose and 1 mM dithioerythritol resulted in the specific release of 88% of the fumarate reductase activity into the spheroplast medium. Only small amounts of the cytoplasmic proteins malic enzyme and acetate kinase were released during this procedure. There results indicate a peripheral location of the fumarate reductase of C. formicoaceticum on the membrane.
mesh_terms: D000084:Acetate Kinase / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D002474:Cell-Free System; D003013:Clostridium / Q000201:enzymology* / Q000378:metabolism; D005650:Fumarates / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*
chemical_list: D005650:Fumarates; D008293:Malates; D009243:NAD; D010088:Oxidoreductases; D008291:Malate Dehydrogenase; D000084:Acetate Kinase