RuBP was originally discovered by
Andrew Benson in 1951 while working in the lab of
Melvin Calvin at UC Berkeley.[4][5] Calvin, who had been away from the lab at the time of discovery and was not listed as a co-author, controversially removed the full molecule name from the title of the initial paper, identifying it solely as "ribulose".[4][6] At the time, the molecule was known as ribulose diphosphate (RDP or RuDP) but the prefix
di- was changed to
bis- to emphasize the nonadjacency of the two phosphate groups.[4][5][7]
Role in photosynthesis and the Calvin-Benson Cycle
The enzyme ribulose-1,5-bisphosphate carboxylase-oxygenase (
rubisco) catalyzes the reaction between RuBP and
carbon dioxide. The product is the highly unstable six-carbon intermediate known as 3-keto-2-carboxyarabinitol 1,5-bisphosphate, or 2'-carboxy-3-keto-D-arabinitol 1,5-bisphosphate (CKABP).[8] This six-carbon
β-ketoacid intermediate hydrates into another six-carbon intermediate in the form of a
gem-diol.[9] This intermediate then cleaves into two molecules of
3-phosphoglycerate (3-PGA) which is used in a number of metabolic pathways and is converted into glucose.[10][11]
RuBP acts as an
enzyme inhibitor for the enzyme rubisco, which regulates the net activity of carbon fixation.[13][14][15] When RuBP is bound to an active site of rubisco, the ability to activate via carbamylation with CO2 and Mg2+ is blocked. The functionality of rubisco activase involves removing RuBP and other inhibitory bonded molecules to re-enable carbamylation on the active site.[1]: 5
Rubisco also catalyzes RuBP with oxygen (O 2) in an interaction called
photorespiration, a process that is more prevalent at high temperatures.[16][17] During photorespiration RuBP combines with O 2 to become 3-PGA and phosphoglycolic acid.[18][19][20] Like the Calvin-Benson Cycle, the photorespiratory pathway has been noted for its enzymatic inefficiency[19][20] although this characterization of the
enzymatic kinetics of rubisco have been contested.[21] Due to enhanced RuBP carboxylation and decreased rubisco oxygenation stemming from the increased concentration of CO2 in the
bundle sheath, rates of photorespiration are decreased in
C4 plants.[1]: 103 Similarly, photorespiration is limited in
CAM photosynthesis due to kinetic delays in enzyme activation, again stemming from the ratio of carbon dioxide to oxygen.[22]
Measurement
RuBP can be
measured isotopically via the conversion of 14CO2 and RuBP into
glyceraldehyde 3-phosphate.[23] G3P can then be measured using an
enzymatic optical assay.[23][24][a] Given the abundance of RuBP in biological samples, an added difficulty is distinguishing particular reservoirs of the substrate, such as the RuBP internal to a chloroplast vs external. One approach to resolving this is by subtractive inference, or measuring the total RuBP of a system, removing a reservoir (e.g. by centrifugation), re-measuring the total RuBP, and using the difference to infer the concentration in the given repository.[25]
^Nelson, D. L.; Cox, M. M. (2000). Lehninger, Principles of Biochemistry (3rd ed.). New York: Worth Publishing.
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^Tabita, F. R. (1999). "Microbial ribulose 1,5-bisphosphate carboxylase/oxygenase: A different perspective". Photosynthesis Research. 60: 1–28.
doi:
10.1023/A:1006211417981.
S2CID21975329.
^
abBenson, A. A. (1951). "Identificiation of Ribulose in C14O2 Photosynthesis Products". Journal of the American Chemical Society. 73 (6): 2971–2972.
doi:
10.1021/ja01150a545.
^Lorimer, G. H.; Andrews, T. J.; et al. (1986). "2´-carboxy-3-keto-D-arabinitol 1,5-bisphosphate, the six-carbon intermediate of the ribulose bisphosphate carboxylase reaction". Phil. Trans. R. Soc. Lond. B. 313 (1162): 397–407.
Bibcode:
1986RSPTB.313..397L.
doi:
10.1098/rstb.1986.0046.
^Mauser, H.; King, W. A.; Gready, J. E.; Andrews, T. J. (2001). "CO2 Fixation by Rubisco: Computational Dissection of the Key Steps of Carboxylation, Hydration, and C−C Bond Cleavage". J. Am. Chem. Soc. 123 (44): 10821–10829.
doi:
10.1021/ja011362p.
PMID11686683.
^Kaiser, G. E.
"Light Independent Reactions". Biol 230: Microbiology. The Community College of Baltimore County, Catonsville Campus. Retrieved 7 May 2021.
^
abHatch, M. D.; Slack, C. R. (1970). "Photosynthetic CO2-Fixation Pathways". Annual Review of Plant Physiology. 21: 141–162.
doi:
10.1146/annurev.pp.21.060170.001041.
^Spreitzer, R. J.; Salvucci, M. E. (2002). "Rubisco: Structure, Regulatory Interactions, and Possibilities for a Better Enzyme". Annual Review of Plant Biology. 53: 449–475.
doi:
10.1146/annurev.arplant.53.100301.135233.
PMID12221984.
^Taylor, Thomas C.; Andersson, Inger (1997). "The structure of the complex between rubisco and its natural substrate ribulose 1,5-bisphosphate". Journal of Molecular Biology. 265 (4): 432–444.
doi:
10.1006/jmbi.1996.0738.
PMID9034362.
^Keys, A. J.; Sampaio, E. V. S. B.; et al. (1977). "Effect of Temperature on Photosynthesis and Photorespiration of Wheat Leaves". Journal of Experimental Botany. 28 (3): 525–533.
doi:
10.1093/jxb/28.3.525.
^Sharkey, T. D. (1988). "Estimating the rate of photorespiration in leaves". Physiologia Plantarum. 73 (1): 147–152.
doi:
10.1111/j.1399-3054.1988.tb09205.x.
^
abKebeish, R.; Niessen, M.; et al. (2007). "Chloroplastic photorespiratory bypass increases photosynthesis and biomass production in Arabidopsis thaliana". Nature Biotechnology. 25 (5): 593–599.
doi:
10.1038/nbt1299.
PMID17435746.
S2CID22879451.
^Niewiadomska, E.; Borland, A. M. (2008). "Crassulacean Acid Metabolism: A Cause or Consequence of Oxidative Stress in Planta?". In Lüttge, U.; Beyschlag, W.; Murata, J. (eds.). Progress in Botany. Vol. 69. pp. 247–266.
doi:
10.1007/978-3-540-72954-9_10.
ISBN978-3-540-72954-9.
^
abLatzko, E.; Gibbs, M. (1972). "Measurement of the intermediates of the photosynthetic carbon reduction cycle, using enzymatic methods". Photosynthesis and Nitrogen Fixation Part B. Methods in Enzymology. Vol. 24. Academic Press. pp. 261–268.
doi:
10.1016/0076-6879(72)24073-3.
ISBN9780121818876.
ISSN0076-6879.
PMID4670193.