If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: photosynthetic dark reactions, photosynthetic CO2 fixation, reductive pentose phosphate pathway, Calvin cycle, photosynthesis - dark reaction, carbon fixation, Calvin-Benson cycle
|Superclasses:||Biosynthesis → Carbohydrates Biosynthesis → Sugars Biosynthesis|
|Degradation/Utilization/Assimilation → C1 Compounds Utilization and Assimilation → CO2 Fixation → Autotrophic CO2 Fixation|
|Generation of Precursor Metabolites and Energy → Photosynthesis|
Some taxa known to possess this pathway include : Arabidopsis thaliana col, Arabidopsis thaliana Ws, Chlamydomonas reinhardtii, Nicotiana tabacum, Synechococcus elongatus PCC 7942, Synechocystis sp. PCC 6803
Expected Taxonomic Range:
The Calvin cycle is the major CO2 fixation pathway, found in all in green plants and many autotrophic bacteria.
In this cycle, one CO2 molecule at a time is added to the acceptor molecule D-ribulose-1,5-bisphosphate (RuBP) generating two molecules of 3-phospho-D-glycerate. The 3-phospho-D-glycerate is then passed through a cyclic series of reactions in which the acceptor molecule (RuBP) is regenerated. Out of the six carbons present in two molecules of 3-phospho-D-glycerate, five are recycled and only one remains available for biosynthesis. Since in each turn of the cycle only one carbon atom is assimilated, the cycle must go through three turns to produce one molecule of 3-phospho-D-glycerate, or six turns to produce one molecule of a hexose sugar.
The Calvin cycle can be divided into three stages: fixation, reduction and regeneration.
In the first stage the reductive carboxylation of D-ribulose-1,5-bisphosphate (RuBP) is catalyzed by the the enzyme ribulose bisphosphate carboxylase (RubisCO), forming 2 molecules of 3-phospho-D-glycerate.
In the second stage these two molecules are phosphorylated to 1,3-bisphospho-D-glycerate and then reductively dephosphorylated to D-glyceraldehyde 3-phosphate. In three turns of the cycle 3 molecules of CO2 are fixed, and 6 molecules of D-glyceraldehyde 3-phosphate are formed. Out of these, one is diverted to biosynthetic pathways, while the other 5 are used up in the next stage.
The third stage is the most complicated one. It consists of a series of rearrangements that eventually regenerate RuBP. Some of the D-glyceraldehyde 3-phosphate molecules are converted to glycerone phosphate. D-glyceraldehyde 3-phosphate and glycerone phosphate are then condensed into fructose 1,6-bisphosphate which is dephosphorylated to β-D-fructofuranose 6-phosphate. β-D-fructofuranose 6-phosphate is then combined with another D-glyceraldehyde 3-phosphate molecule and cleaved into D-xylulose 5-phosphate (X5P) and D-erythrose 4-phosphate. The later is combined with glycerone phosphate forming D-sedoheptulose-1,7-bisphosphate, which is dephosphorylated to D-sedoheptulose 7-phosphate. D-sedoheptulose 7-phosphate is combined with D-glyceraldehyde 3-phosphate and is cleaved into a second D-xylulose 5-phosphate and a D-ribose 5-phosphate (R5P). Both of these are converted into D-ribulose 5-phosphate, which is finally phosphorylated to D-ribulose-1,5-bisphosphate, regenerating the key CO2-acceptor molecule.
During this cycle, especially during the day, 3-phospho-D-glycerate, glycerone phosphate, or D-glyceraldehyde 3-phosphate can be siphoned off and sent out to the cytosol via the triose phosphates transporter for sucrose biosynthesis I (from photosynthesis). Plants need to carefully control the carbon flux between this and competeing pathways to make sure that the Calvin cycle can proceed [Serrato09].
Sitt91: Sitt, M, Quick, WP, Schurr U, Schulze ED, Rodermel SR, Bogorad L (1991). "Decreased ribulose-1,5-bisphosphate carboxylase-oxygenase in transgenic tobacco transformed with 'antisense' rbcS II. Flux-control coefficients for photosynthesis in varying light, CO2, and air humidity." Planta, 183:555-566.
Alvarez98: Alvarez M, Zeelen JP, Mainfroid V, Rentier-Delrue F, Martial JA, Wyns L, Wierenga RK, Maes D (1998). "Triose-phosphate isomerase (TIM) of the psychrophilic bacterium Vibrio marinus. Kinetic and structural properties." J Biol Chem 273(4);2199-206. PMID: 9442062
Amichay93: Amichay D, Levitz R, Gurevitz M (1993). "Construction of a Synechocystis PCC6803 mutant suitable for the study of variant hexadecameric ribulose bisphosphate carboxylase/oxygenase enzymes." Plant Mol Biol 23(3);465-76. PMID: 8219082
Baldwin78: Baldwin SA, Perham RN (1978). "Novel kinetic and structural properties of the class-I D-fructose 1,6-bisphosphate aldolase from Escherichia coli (Crookes' strain)." Biochem J 1978;169(3);643-52. PMID: 348198
Baldwin78a: Baldwin SA, Perham RN, Stribling D (1978). "Purification and characterization of the class-II D-fructose 1,6-bisphosphate aldolase from Escherichia coli (Crookes' strain)." Biochem J 1978;169(3);633-41. PMID: 417719
Beaucamp97: Beaucamp N, Hofmann A, Kellerer B, Jaenicke R (1997). "Dissection of the gene of the bifunctional PGK-TIM fusion protein from the hyperthermophilic bacterium Thermotoga maritima: design and characterization of the separate triosephosphate isomerase." Protein Sci 1997;6(10);2159-65. PMID: 9336838
Beaucamp97a: Beaucamp N, Schurig H, Jaenicke R (1997). "The PGK-TIM fusion protein from Thermotoga maritima and its constituent parts are intrinsically stable and fold independently." Biol Chem 1997;378(7);679-85. PMID: 9278147
Berthiaume89: Berthiaume L, Beaudry D, Lazure C, Tolan DR, Sygusch J (1989). "Recombinant anaerobic maize aldolase: overexpression, characterization, and metabolic implications." Arch Biochem Biophys 272(2);281-9. PMID: 2751305
Branny98: Branny P, de la Torre F, Garel JR (1998). "An operon encoding three glycolytic enzymes in Lactobacillus delbrueckii subsp. bulgaricus: glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase and triosephosphate isomerase." Microbiology 144 ( Pt 4);905-14. PMID: 9579064
Brown09: Brown G, Singer A, Lunin VV, Proudfoot M, Skarina T, Flick R, Kochinyan S, Sanishvili R, Joachimiak A, Edwards AM, Savchenko A, Yakunin AF (2009). "Structural and biochemical characterization of the type II fructose-1,6-bisphosphatase GlpX from Escherichia coli." J Biol Chem 284(6);3784-92. PMID: 19073594
Cancilla95: Cancilla MR, Davidson BE, Hillier AJ, Nguyen NY, Thompson J (1995). "The Lactococcus lactis triosephosphate isomerase gene, tpi, is monocistronic." Microbiology 141 ( Pt 1);229-38. PMID: 7534588
Chiadmi99: Chiadmi M, Navaza A, Miginiac-Maslow M, Jacquot JP, Cherfils J (1999). "Redox signalling in the chloroplast: structure of oxidized pea fructose-1,6-bisphosphate phosphatase." EMBO J 18(23);6809-15. PMID: 10581254
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