Publications

• Malonyl-coenzyme A reductase in the modified 3-hydroxypropionate cycle for autotrophic carbon fixation in archaeal Metallosphaera and Sulfolobus spp.

  Alber B., Olinger M., Rieder A., Kockelkorn D., Jobst B., Hugler M., Fuchs G.

  Autotrophic members of the Sulfolobales (Crenarchaeota) contain acetyl-coenzyme A (CoA)/propionyl-CoA carboxylase as the CO2 fixation enzyme and use a modified 3-hydroxypropionate cycle to assimilate CO2 into cell material. In this central metabolic pathway malonyl-CoA, the product of acetyl-CoA c ... >> More

  Autotrophic members of the Sulfolobales (Crenarchaeota) contain acetyl-coenzyme A (CoA)/propionyl-CoA carboxylase as the CO2 fixation enzyme and use a modified 3-hydroxypropionate cycle to assimilate CO2 into cell material. In this central metabolic pathway malonyl-CoA, the product of acetyl-CoA carboxylation, is further reduced to 3-hydroxypropionate. Extracts of Metallosphaera sedula contained NADPH-specific malonyl-CoA reductase activity that was 10-fold up-regulated under autotrophic growth conditions. Malonyl-CoA reductase was partially purified and studied. Based on N-terminal amino acid sequencing the corresponding gene was identified in the genome of the closely related crenarchaeum Sulfolobus tokodaii. The Sulfolobus gene was cloned and heterologously expressed in Escherichia coli, and the recombinant protein was purified and studied. The enzyme catalyzes the following reaction: malonyl-CoA + NADPH + H+ --> malonate-semialdehyde + CoA + NADP+. In its native state it is associated with small RNA. Its activity was stimulated by Mg2+ and thiols and inactivated by thiol-blocking agents, suggesting the existence of a cysteine adduct in the course of the catalytic cycle. The enzyme was specific for NADPH (Km = 25 microM) and malonyl-CoA (Km = 40 microM). Malonyl-CoA reductase has 38% amino acid sequence identity to aspartate-semialdehyde dehydrogenase, suggesting a common ancestor for both proteins. It does not exhibit any significant similarity with malonyl-CoA reductase from Chloroflexus aurantiacus. This shows that the autotrophic pathway in Chloroflexus and Sulfolobaceae has evolved convergently and that these taxonomic groups have recruited different genes to bring about similar metabolic processes. << Less

  J. Bacteriol. 188:8551-8559(2006) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• A 3-hydroxypropionate/4-hydroxybutyrate autotrophic carbon dioxide assimilation pathway in Archaea.

  Berg I.A., Kockelkorn D., Buckel W., Fuchs G.

  The assimilation of carbon dioxide (CO2) into organic material is quantitatively the most important biosynthetic process. We discovered that an autotrophic member of the archaeal order Sulfolobales, Metallosphaera sedula, fixed CO2 with acetyl-coenzyme A (acetyl-CoA)/propionyl-CoA carboxylase as t ... >> More

  The assimilation of carbon dioxide (CO2) into organic material is quantitatively the most important biosynthetic process. We discovered that an autotrophic member of the archaeal order Sulfolobales, Metallosphaera sedula, fixed CO2 with acetyl-coenzyme A (acetyl-CoA)/propionyl-CoA carboxylase as the key carboxylating enzyme. In this system, one acetyl-CoA and two bicarbonate molecules were reductively converted via 3-hydroxypropionate to succinyl-CoA. This intermediate was reduced to 4-hydroxybutyrate and converted into two acetyl-CoA molecules via 4-hydroxybutyryl-CoA dehydratase. The key genes of this pathway were found not only in Metallosphaera but also in Sulfolobus, Archaeoglobus, and Cenarchaeum species. Moreover, the Global Ocean Sampling database contains half as many 4-hydroxybutyryl-CoA dehydratase sequences as compared with those found for another key photosynthetic CO2-fixing enzyme, ribulose-1,5-bisphosphate carboxylase-oxygenase. This indicates the importance of this enzyme in global carbon cycling. << Less

  Science 318:1782-1786(2007) [PubMed] [EuropePMC]

  This publication is cited by 6 other entries.

• Purification and characterization of a coenzyme-A-dependent succinate-semialdehyde dehydrogenase from Clostridium kluyveri.

  Soehling B., Gottschalk G.

  Cell extracts of Clostridium kluyveri, grown on ethanol plus succinate contained a succinyl-CoA:CoA transferase (0.28 U/mg), a coenzyme-A-dependent succinate-semialdehyde dehydrogenase (0.73 U/mg) and a NAD(+)-dependent 4-hydroxybutyrate dehydrogenase (0.25 U/mg). The semialdehyde dehydrogenase, w ... >> More

  Cell extracts of Clostridium kluyveri, grown on ethanol plus succinate contained a succinyl-CoA:CoA transferase (0.28 U/mg), a coenzyme-A-dependent succinate-semialdehyde dehydrogenase (0.73 U/mg) and a NAD(+)-dependent 4-hydroxybutyrate dehydrogenase (0.25 U/mg). The semialdehyde dehydrogenase, which catalyzed the NADPH-dependent reduction of succinyl-CoA to succinate semialdehyde, was purified 59-fold to homogeneity. A molecular mass of 115000 Da was determined for the native enzyme; SDS/PAGE revealed one protein band at 55,000, indicating that the active form is a dimer. The enzyme was highly specific for succinyl-CoA and succinate semialdehyde. The pH optimum was 7.0 for the reduction of succinyl-CoA, and 8.5 for the reverse reaction. Km values were determined for both the forward and reverse directions. The kinetic data suggest a ping-pong mechanism. << Less

  Eur. J. Biochem. 212:121-127(1993) [PubMed] [EuropePMC]