RuBP was originally discovered byAndrew Benson in 1951 while working in the lab ofMelvin 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 asribulose diphosphate (RDP or RuDP) but the prefixdi- was changed tobis- 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 andcarbon 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-carbonβ-ketoacid intermediate hydrates into another six-carbon intermediate in the form of agem-diol.[9] This intermediate then cleaves into two molecules of3-phosphoglycerate (3-PGA) which is used in a number of metabolic pathways and is converted into glucose.[10][11]
RuBP acts as anenzyme 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 withCO2 andMg2+ 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 calledphotorespiration, a process that is more prevalent at high temperatures.[16][17] During photorespiration RuBP combines withO 2 to become 3-PGA andphosphoglycolic 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 theenzymatic kinetics of rubisco has been contested.[21] Due to enhanced RuBP carboxylation and decreased rubisco oxygenation stemming from the increased concentration ofCO2 in thebundle sheath, rates of photorespiration are decreased inC4 plants.[1]: 103 Similarly, photorespiration is limited inCAM photosynthesis due to kinetic delays in enzyme activation, again stemming from the ratio of carbon dioxide to oxygen.[22]
RuBP can bemeasured isotopically via the conversion of14CO2 and RuBP intoglyceraldehyde 3-phosphate.[23] G3P can then be measured using anenzymatic 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.ISBN1-57259-153-6.
^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. Archived fromthe original on 9 May 2021. Retrieved7 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 inArabidopsis 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.
