Ribulose 1,5-bisphosphate

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Ribulose bisphosphate
)
Ribulose 1,5-bisphosphate
Skeletal formula of RuBP
The acid form of the RuBP anion
Ball-and-stick model, based on x-ray diffraction data
Names
IUPAC name
1,5-Di-O-phosphono-D-ribulose
Other names
Ribulose 1,5-diphosphate
Identifiers
3D model (
JSmol
)
ChEBI
ChemSpider
KEGG
UNII
  • InChI=1S/C5H12O11P2/c6-3(1-15-17(9,10)11)5(8)4(7)2-16-18(12,13)14/h3,5-6,8H,1-2H2,(H2,9,10,11)(H2,12,13,14)/t3-,5-/m1/s1 checkY
    Key: YAHZABJORDUQGO-NQXXGFSBSA-N checkY
  • O=P(O)(OCC(=O)[C@H](O)[C@H](O)COP(=O)(O)O)O
Properties
C5H12O11P2
Molar mass 310.088 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Ribulose 1,5-bisphosphate (RuBP) is an

Eukarya.[3]

History

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

See also:
Calvin-Benson Cycle

The enzyme ribulose-1,5-bisphosphate carboxylase-oxygenase (

3-phosphoglycerate (3-PGA) which is used in a number of metabolic pathways and is converted into glucose.[10][11]

In the

ribulose-5-phosphate (produced by glyceraldehyde 3-phosphate) by ATP.[11][12]

The Calvin-Benson cycle showing the role of ribulose-1,5-bisphosphate.

Interactions with rubisco

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 

Role in photorespiration

See also: Photorespiration

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]

See also

References

  1. ^
    ISBN 978-0-7923-6143-5
    .
  2. ISBN 1-57259-153-6
    .
  3. S2CID 21975329
    .
  4. ^
    S2CID 53092349
    .
  5. ^
    doi:10.1021/ja01150a545
    .
  6. ISBN 978-1-4020-3324-7
    .
  7. S2CID 7622999
    .
  8. doi:10.1098/rstb.1986.0046
    .
  9. PMID 11686683
    .
  10. ^ Kaiser, G. E. "Light Independent Reactions". Biol 230: Microbiology. The Community College of Baltimore County, Catonsville Campus. Retrieved 7 May 2021.
  11. ^
    doi:10.1146/annurev.pp.21.060170.001041
    .
  12. ISBN 978-1-63635-041-7
    .
  13. PMID 6417133
    .
  14. PMID 12221984
    .
  15. PMID 9034362
    .
  16. ISBN 978-0-7923-4316-5
    .
  17. doi:10.1093/jxb/28.3.525
    .
  18. doi:10.1111/j.1399-3054.1988.tb09205.x
    .
  19. ^
    S2CID 22879451
    .
  20. ^
    JSTOR 23694986
    .
  21. S2CID 3718311
    .
  22. ISBN 978-3-540-72954-9
    .
  23. ^
    PMID 4670193
    .
  24. PMID 16657074
    .
  25. PMID 16661073
    .
  1. ^ Note that G3P is a 3-carbon sugar so its abundance should be twice that of the 6-carbon RuBP, after accounting for rates of enzymatic catalysis.
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