ENTRY ko00720 Pathway NAME Other carbon fixation pathways DESCRIPTION Carbon fixation is an important pathway for autotrophs living in various environments. Plants and cyanobacteria fix CO2 as organic compounds using solar energy mainly by the reductive pentose phosphate cycle (also called Calvin cycle, Calvin-Benson cycle, or Calvin-Benson-Bassham cycle) [MD:M00165]. There are, at least, five additional carbon fixation pathways known to exist in autotrophic bacteria and archaea, which differ in reducing compounds, energy source, and oxygen sensitivity of enzymes. (i) The reductive citric acid cycle (Arnon-Buchanan cycle) [MD:M00173] is found in microaerophiles and anaerobes, such as green sulfur bacteria. In one complete turn of this cycle, four molecules of CO2 are fixed by the enzymes that are sensitive to oxygen, resulting in the production of one molecule of oxaloacetate, which is itself an intermediate of the cycle. (ii) The reductive acetyl-CoA pathway (Wood-Ljungdahl pathway) [MD:M00377] is found in strictly anaerobic bacteria and archaea (Proteobacteria, Planctomycetes, Spirochaetes, and Euryarchaeota), some of which are methane-forming. A bifunctional enzyme, carbon monoxide dehydrogenase/acetyl-CoA synthase, catalyzes the reactions from CO2 to CO and from CO2 to a methyl group, and then to generate acetyl-CoA. (iii) The 3-hydroxypropionate bicycle [MD:M00376] is found in some green non-sulphur bacteria of the family Chloroflexaceae. In one complete turn of this bicycle, three molecules of bicarbonate are converted into one molecule of pyruvate. In addition, this bicycle provides the secondary benefit of useful intermediates for biosynthesis: acetyl-CoA, glyoxylate, and succinyl-CoA. (iv) The hydroxypropionate-hydroxybutyrate cycle [MD:M00375] is found in aerobic Crenarchaeota, Acidianus, Metallosphaera, and Sulfolobales. Some of the intermediates and the carboxylation reactions are the same as in the 3-hydroxypropionate bicycle. One complete turn of this cycle generates two molecules of acetyl-CoA, one of which is reutilized in the the cycle and the other is removed for cell material biosynthesis. (v) The dicarboxylate-hydroxybutyrate cycle [MD:M00374] was named after its intermediates: succinate (a kind of dicarboxylate) and hydroxybutyrate. This cycle has been found only in Ignicoccus hospitals, a strictly anaerobic hyperthermophilic archaea. Recent genome study suggests that this cycle may exist in Desulfurococcales (to which Ignicoccus belongs) and Thermoproteales (a taxon close to the origin of archaea). The first half of the cycle, from acetyl-CoA to succinate-CoA, corresponds to the reductive citric acid cycle and the latter half of the cycle, from succinate-CoA to two molecules of acetyl-CoA, corresponds to the hydroxypropionate-hydroxybutyrate cycle. CLASS Metabolism; Energy metabolism PATHWAY_MAP ko00720 Other carbon fixation pathways MODULE M00173 Reductive citrate cycle (Arnon-Buchanan cycle) [PATH:ko00720] M00374 Dicarboxylate-hydroxybutyrate cycle [PATH:ko00720] M00375 Hydroxypropionate-hydroxybutylate cycle [PATH:ko00720] M00376 3-Hydroxypropionate bi-cycle [PATH:ko00720] M00377 Reductive acetyl-CoA pathway (Wood-Ljungdahl pathway) [PATH:ko00720] M00579 Phosphate acetyltransferase-acetate kinase pathway, acetyl-CoA => acetate [PATH:ko00720] M00620 Incomplete reductive citrate cycle, acetyl-CoA => oxoglutarate [PATH:ko00720] DBLINKS GO: 0015977 ORTHOLOGY K00169 pyruvate ferredoxin oxidoreductase alpha subunit [EC:1.2.7.1] K00170 pyruvate ferredoxin oxidoreductase beta subunit [EC:1.2.7.1] K00172 pyruvate ferredoxin oxidoreductase gamma subunit [EC:1.2.7.1] K00189 2-oxoisovalerate/pyruvate ferredoxin oxidoreductase gamma subunit [EC:1.2.7.7 1.2.7.1] K00171 pyruvate ferredoxin oxidoreductase delta subunit [EC:1.2.7.1] K03737 pyruvate-ferredoxin/flavodoxin oxidoreductase [EC:1.2.7.1 1.2.7.-] K01007 pyruvate, water dikinase [EC:2.7.9.2] K01006 pyruvate, orthophosphate dikinase [EC:2.7.9.1] K01595 phosphoenolpyruvate carboxylase [EC:4.1.1.31] K01958 pyruvate carboxylase [EC:6.4.1.1] K01959 pyruvate carboxylase subunit A [EC:6.4.1.1] K01960 pyruvate carboxylase subunit B [EC:6.4.1.1] K00024 malate dehydrogenase [EC:1.1.1.37] K01676 fumarate hydratase, class I [EC:4.2.1.2] K01677 fumarate hydratase subunit alpha [EC:4.2.1.2] K01678 fumarate hydratase subunit beta [EC:4.2.1.2] K01679 fumarate hydratase, class II [EC:4.2.1.2] K01675 fumarate hydratase D [EC:4.2.1.2] K01774 fumarate hydratase E [EC:4.2.1.2] K00239 succinate dehydrogenase flavoprotein subunit [EC:1.3.5.1] K00240 succinate dehydrogenase iron-sulfur subunit [EC:1.3.5.1] K00241 succinate dehydrogenase cytochrome b subunit K00242 succinate dehydrogenase membrane anchor subunit K18859 succinate dehydrogenase subunit D K18860 succinate dehydrogenase subunit D K00244 succinate dehydrogenase flavoprotein subunit [EC:1.3.5.1] K00245 succinate dehydrogenase iron-sulfur subunit [EC:1.3.5.1] K00246 succinate dehydrogenase subunit C K00247 succinate dehydrogenase subunit D K00233 succinate dehydrogenase flavoprotein subunit [EC:1.3.5.1 7.1.1.12] K25995 succinate dehydrogenase iron-sulfur subunit [EC:1.3.5.1 7.1.1.12] K25996 succinate dehydrogenase subunit C K26318 fumarate reductase (cytochrome) [EC:1.3.2.4] K18556 NADH-dependent fumarate reductase subunit A [EC:1.3.1.6] K18557 NADH-dependent fumarate reductase subunit B [EC:1.3.1.6] K18558 NADH-dependent fumarate reductase subunit C K18559 NADH-dependent fumarate reductase subunit D K18560 NADH-dependent fumarate reductase subunit E K18209 fumarate reductase (CoM/CoB) subunit A [EC:1.3.4.1] K18210 fumarate reductase (CoM/CoB) subunit B [EC:1.3.4.1] K01902 succinyl-CoA synthetase alpha subunit [EC:6.2.1.5] K01903 succinyl-CoA synthetase beta subunit [EC:6.2.1.5] K15038 succinyl-CoA reductase [EC:1.2.1.76] K14465 succinate semialdehyde reductase (NADPH) [EC:1.1.1.-] K14466 4-hydroxybutyrate---CoA ligase (AMP-forming) [EC:6.2.1.40] K14467 4-hydroxybutyrate---CoA ligase (AMP-forming) [EC:6.2.1.40] K18861 4-hydroxybutyrate---CoA ligase (AMP-forming) [EC:6.2.1.40] K25774 4-hydroxybutyrate---CoA ligase (AMP-forming) [EC:6.2.1.40] K18593 4-hydroxybutyrate---CoA ligase (ADP-forming) [EC:6.2.1.56] K14534 4-hydroxybutyryl-CoA dehydratase / vinylacetyl-CoA-Delta-isomerase [EC:4.2.1.120 5.3.3.3] K15016 enoyl-CoA hydratase / 3-hydroxyacyl-CoA dehydrogenase [EC:4.2.1.17 1.1.1.35] K00626 acetyl-CoA C-acetyltransferase [EC:2.3.1.9] K00174 2-oxoglutarate/2-oxoacid ferredoxin oxidoreductase subunit alpha [EC:1.2.7.3 1.2.7.11] K00175 2-oxoglutarate/2-oxoacid ferredoxin oxidoreductase subunit beta [EC:1.2.7.3 1.2.7.11] K00177 2-oxoglutarate ferredoxin oxidoreductase subunit gamma [EC:1.2.7.3] K00176 2-oxoglutarate ferredoxin oxidoreductase subunit delta [EC:1.2.7.3] K00031 isocitrate dehydrogenase [EC:1.1.1.42] K01681 aconitate hydratase [EC:4.2.1.3] K27802 aconitate hydratase A / 2-methylisocitrate dehydratase [EC:4.2.1.3 4.2.1.99] K01682 aconitate hydratase 2 / 2-methylisocitrate dehydratase [EC:4.2.1.3 4.2.1.99] K01648 ATP citrate (pro-S)-lyase [EC:2.3.3.8] K15230 ATP-citrate lyase alpha-subunit [EC:2.3.3.8] K15231 ATP-citrate lyase beta-subunit [EC:2.3.3.8] K15232 citryl-CoA synthetase large subunit [EC:6.2.1.18] K15233 citryl-CoA synthetase small subunit K15234 citryl-CoA lyase [EC:4.1.3.34] K01962 acetyl-CoA carboxylase carboxyl transferase subunit alpha [EC:6.4.1.2 2.1.3.15] K02160 acetyl-CoA carboxylase biotin carboxyl carrier protein K01961 acetyl-CoA carboxylase, biotin carboxylase subunit [EC:6.4.1.2 6.3.4.14] K01963 acetyl-CoA carboxylase carboxyl transferase subunit beta [EC:6.4.1.2 2.1.3.15] K01964 acetyl-CoA/propionyl-CoA carboxylase [EC:6.4.1.2 6.4.1.3] K18603 acetyl-CoA/propionyl-CoA carboxylase [EC:6.4.1.2 6.4.1.3] K15036 acetyl-CoA/propionyl-CoA carboxylase [EC:6.4.1.2 6.4.1.3 2.1.3.15] K18604 acetyl-CoA/propionyl-CoA carboxylase [EC:6.4.1.2 6.4.1.3 2.1.3.15] K15037 biotin carboxyl carrier protein K18605 biotin carboxyl carrier protein K14468 malonyl-CoA reductase / 3-hydroxypropionate dehydrogenase (NADP+) [EC:1.2.1.75 1.1.1.298] K15017 malonyl-CoA/succinyl-CoA reductase (NADPH) [EC:1.2.1.75 1.2.1.76] K15039 3-hydroxypropionate dehydrogenase (NADP+) [EC:1.1.1.298] K18602 malonic semialdehyde reductase [EC:1.1.1.-] K14469 acrylyl-CoA reductase (NADPH) / 3-hydroxypropionyl-CoA dehydratase / 3-hydroxypropionyl-CoA synthetase [EC:1.3.1.84 4.2.1.116 6.2.1.36] K15018 3-hydroxypropionyl-coenzyme A synthetase [EC:6.2.1.36] K18594 3-hydroxypropionyl-CoA synthetase (ADP-forming) [EC:6.2.1.-] K15019 3-hydroxypropionyl-coenzyme A dehydratase [EC:4.2.1.116] K15020 acryloyl-coenzyme A reductase [EC:1.3.1.84] K08691 malyl-CoA/(S)-citramalyl-CoA lyase [EC:4.1.3.24 4.1.3.25] K14449 2-methylfumaryl-CoA hydratase [EC:4.2.1.148] K14470 2-methylfumaryl-CoA isomerase [EC:5.4.1.3] K09709 3-methylfumaryl-CoA hydratase [EC:4.2.1.153] K15052 propionyl-CoA carboxylase [EC:6.4.1.3 2.1.3.15] K05606 methylmalonyl-CoA/ethylmalonyl-CoA epimerase [EC:5.1.99.1] K01847 methylmalonyl-CoA mutase [EC:5.4.99.2] K01848 methylmalonyl-CoA mutase, N-terminal domain [EC:5.4.99.2] K01849 methylmalonyl-CoA mutase, C-terminal domain [EC:5.4.99.2] K14471 succinyl-CoA:(S)-malate CoA-transferase subunit A [EC:2.8.3.22] K14472 succinyl-CoA:(S)-malate CoA-transferase subunit B [EC:2.8.3.22] K05299 formate dehydrogenase (NADP+) alpha subunit [EC:1.17.1.10] K15022 formate dehydrogenase (NADP+) beta subunit [EC:1.17.1.10] K22015 formate dehydrogenase (hydrogenase) [EC:1.17.98.4 1.17.98.-] K25123 iron hydrogenase HydA2 [EC:1.12.7.-] K25124 FeS-containing electron transfer protein K01938 formate--tetrahydrofolate ligase [EC:6.3.4.3] K01491 methylenetetrahydrofolate dehydrogenase (NADP+) / methenyltetrahydrofolate cyclohydrolase [EC:1.5.1.5 3.5.4.9] K01500 methenyltetrahydrofolate cyclohydrolase [EC:3.5.4.9] K00297 methylenetetrahydrofolate reductase (NADH) [EC:1.5.1.54] K25007 methylenetetrahydrofolate reductase (NADH) small subunit K25008 ion-translocating oxidoreductase complex subunit C [EC:7.-.-.-] K15023 5-methyltetrahydrofolate corrinoid/iron sulfur protein methyltransferase [EC:2.1.1.258] K25221 [methyl-Co(III) glycine betaine-specific corrinoid protein]---tetrahydrofolate methyltransferase [EC:2.1.1.378] K25915 [methyl-Co(III) methoxylated-aromatic-compound-specific corrinoid protein]---tetrahydrofolate methyltransferase [EC:2.1.1.385] K26930 [methyl-Co(III) quaternary-amine-specific corrinoid protein]---tetrahydrofolate methyltransferase [EC:2.1.1.389] K00198 anaerobic carbon-monoxide dehydrogenase catalytic subunit [EC:1.2.7.4] K00196 anaerobic carbon-monoxide dehydrogenase iron sulfur subunit K14138 acetyl-CoA synthase [EC:2.3.1.169] K00197 acetyl-CoA decarbonylase/synthase, CODH/ACS complex subunit gamma [EC:2.1.1.245] K00194 acetyl-CoA decarbonylase/synthase, CODH/ACS complex subunit delta [EC:2.1.1.245] K00625 phosphate acetyltransferase [EC:2.3.1.8] K13788 phosphate acetyltransferase [EC:2.3.1.8] K15024 putative phosphotransacetylase [EC:2.3.1.8] K00925 acetate kinase [EC:2.7.2.1] K01895 acetyl-CoA synthetase [EC:6.2.1.1] COMPOUND C00011 CO2 C00022 Pyruvate C00024 Acetyl-CoA C00026 2-Oxoglutarate C00033 Acetate C00036 Oxaloacetate C00042 Succinate C00048 Glyoxylate C00058 Formate C00074 Phosphoenolpyruvate C00083 Malonyl-CoA C00091 Succinyl-CoA C00100 Propanoyl-CoA C00101 Tetrahydrofolate C00122 Fumarate C00143 5,10-Methylenetetrahydrofolate C00149 (S)-Malate C00158 Citrate C00222 3-Oxopropanoate C00227 Acetyl phosphate C00232 Succinate semialdehyde C00234 10-Formyltetrahydrofolate C00237 CO C00288 HCO3- C00311 Isocitrate C00332 Acetoacetyl-CoA C00417 cis-Aconitate C00440 5-Methyltetrahydrofolate C00445 5,10-Methenyltetrahydrofolate C00566 (3S)-Citryl-CoA C00683 (S)-Methylmalonyl-CoA C00877 Crotonoyl-CoA C00894 Propenoyl-CoA C00989 4-Hydroxybutanoic acid C01011 (3S)-Citramalyl-CoA C01013 3-Hydroxypropanoate C01144 (S)-3-Hydroxybutanoyl-CoA C01213 (R)-Methylmalonyl-CoA C04348 L-Malyl-CoA C05668 3-Hydroxypropionyl-CoA C06027 L-erythro-3-Methylmalyl-CoA C06028 2-Methylfumaryl-CoA C11062 4-Hydroxybutyryl-CoA C18323 3-Methylfumaryl-CoA REFERENCE PMID:19955419 AUTHORS Zarzycki J, Brecht V, Muller M, Fuchs G TITLE Identifying the missing steps of the autotrophic 3-hydroxypropionate CO2 fixation cycle in Chloroflexus aurantiacus. JOURNAL Proc Natl Acad Sci U S A 106:21317-22 (2009) DOI:10.1073/pnas.0908356106 REFERENCE PMID:19429610 AUTHORS Teufel R, Kung JW, Kockelkorn D, Alber BE, Fuchs G TITLE 3-hydroxypropionyl-coenzyme A dehydratase and acryloyl-coenzyme A reductase, enzymes of the autotrophic 3-hydroxypropionate/4-hydroxybutyrate cycle in the Sulfolobales. JOURNAL J Bacteriol 191:4572-81 (2009) DOI:10.1128/JB.00068-09 REFERENCE PMID:18511565 AUTHORS Huber H, Gallenberger M, Jahn U, Eylert E, Berg IA, Kockelkorn D, Eisenreich W, Fuchs G TITLE A dicarboxylate/4-hydroxybutyrate autotrophic carbon assimilation cycle in the hyperthermophilic Archaeum Ignicoccus hospitalis. JOURNAL Proc Natl Acad Sci U S A 105:7851-6 (2008) DOI:10.1073/pnas.0801043105 REFERENCE PMID:15838028 AUTHORS Hugler M, Wirsen CO, Fuchs G, Taylor CD, Sievert SM TITLE Evidence for autotrophic CO2 fixation via the reductive tricarboxylic acid cycle by members of the epsilon subdivision of proteobacteria. JOURNAL J Bacteriol 187:3020-7 (2005) DOI:10.1128/JB.187.9.3020-3027.2005 REFERENCE PMID:11827525 AUTHORS Seravalli J, Kumar M, Ragsdale SW TITLE Rapid kinetic studies of acetyl-CoA synthesis: evidence supporting the catalytic intermediacy of a paramagnetic NiFeC species in the autotrophic Wood-Ljungdahl pathway. JOURNAL Biochemistry 41:1807-19 (2002) DOI:10.1021/bi011687i REFERENCE PMID:3096193 AUTHORS Ljungdahl LG TITLE The autotrophic pathway of acetate synthesis in acetogenic bacteria. JOURNAL Annu Rev Microbiol 40:415-50 (1986) DOI:10.1146/annurev.mi.40.100186.002215 REL_PATHWAY ko00710 Carbon fixation by Calvin cycle ///