User:Lluviosa/3-Hydroxypropionate bicycle
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Many photosynthetic life forms (plants, algae, phototrophic and chemoautotrophic bacteria, and archaea) require a way to utilize carbon into their metabolic pathways. This usually occurs in pathways that fix carbon from carbon dioxide (CO2). In the 3-hydroxypropionate bicycle, photosynthetic organisms like Chloroflexus aurantiacus, fix CO2 and bicarbonate (HCO3- ) as part of their metabolic processes.[1]
The Pathway[edit]
The 3-hydroxypropionate bicycle, also known as the 3-hydroxypropionate pathway, is a process that allows some bacteria to generate 3-hydroxypropionate using CO2[2]. It is Divided into two parts or reactions. The overall reaction of the 3-hydroxypropionate pathway is 3 HCO3− + 5 ATP + 6 NADPH + 1 quinone → 1 pyruvate + 6 NADP + 1 quinoneH2 + 3 ADP + 3 phosphate + 2 AMP + 2 pyrophosphate.[3]
Part I[edit]
In part one of the 3-hydroxypropionate pathway CO2 is fixed (i.e. incorporated) by the action of two enzymes, acetyl-CoA carboxylase and propionyl-CoA carboxylase. These enzymes generate malonyl-CoA and (S)-methylmalonyl-CoA, respectively.
Part II[edit]
In part two Malonyl-CoA, in a series of reactions, is further split into acetyl-CoA and glyoxylate. Glyoxylate is incorporated into beta-methylmalyl-coA which is then split, again through a series of reactions, to release pyruvate as well as acetate, which is used to replenish the cycle[3].
Prevalence[edit]
This pathway has been demonstrated in Chloroflexus, a nonsulfur photosynthetic bacterium; however, other studies suggest that 3-hydroxypropionate bicycle is used by several chemotrophic archaea.[4][5] In E. coli 3-hydroxypropionate bicycle has been studied and found to be insensitive to oxygen. This means that within the pathways there is nothing that oxygen can affect because in either part of the pathway or the oxygen is used to drive the reaction forward.[6]
References[edit]
- ^ Tabita, F. Robert (2009-12-15). "The hydroxypropionate pathway of CO 2 fixation: Fait accompli". Proceedings of the National Academy of Sciences. 106 (50): 21015–21016. doi:10.1073/pnas.0912486107. ISSN 0027-8424.
- ^ Herter, Sylvia; Fuchs, Georg; Bacher, Adelbert; Eisenreich, Wolfgang (2002-06). "A Bicyclic Autotrophic CO2 Fixation Pathway in Chloroflexus aurantiacus". Journal of Biological Chemistry. 277 (23): 20277–20283. doi:10.1074/jbc.m201030200. ISSN 0021-9258.
{{cite journal}}: Check date values in:|date=(help)CS1 maint: unflagged free DOI (link) - ^ a b Zarzycki, Jan; Brecht, Volker; Müller, Michael; Fuchs, Georg (2009-12-15). "Identifying the missing steps of the autotrophic 3-hydroxypropionate CO 2 fixation cycle in Chloroflexus aurantiacus". Proceedings of the National Academy of Sciences. 106 (50): 21317–21322. doi:10.1073/pnas.0908356106. ISSN 0027-8424.
{{cite journal}}: line feed character in|title=at position 72 (help) - ^ Tabita, F. Robert (2009-12-15). "The hydroxypropionate pathway of CO 2 fixation: Fait accompli". Proceedings of the National Academy of Sciences. 106 (50): 21015–21016. doi:10.1073/pnas.0912486107. ISSN 0027-8424.
{{cite journal}}: line feed character in|title=at position 36 (help) - ^ Hügler, Michael; Sievert, Stefan M. (2011-01-15). "Beyond the Calvin Cycle: Autotrophic Carbon Fixation in the Ocean". Annual Review of Marine Science. 3 (1): 261–289. doi:10.1146/annurev-marine-120709-142712. ISSN 1941-1405.
- ^ Mattozzi, Matthew d.; Ziesack, Marika; Voges, Mathias J.; Silver, Pamela A.; Way, Jeffrey C. (2013-03-01). "Expression of the sub-pathways of the Chloroflexus aurantiacus 3-hydroxypropionate carbon fixation bicycle in E. coli: Toward horizontal transfer of autotrophic growth". Metabolic Engineering. 16: 130–139. doi:10.1016/j.ymben.2013.01.005. ISSN 1096-7176.