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PHOTORESPIRATION

RUBISCO AND ITS ROLE IN PHOTORESPIRATION WITH DETAILED REACTIONS

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PHOTORESPIRATION

  1. 1. RuBisCo & ITS ROLE IN PHOTORESPIRATION By- Narayan Prahlad.V V Semester Mol.Bio 9/9/2014
  2. 2. Contents  Introduction  RuBisCo  Activation of RuBisCo  Function  Photorespiration  Conclusion  Reference  Acknowledgement
  3. 3. Introduction • Ribulose-1,5 bis phosphate carboxylase/oxidase also abbreviated as RuBisCo - an important plant enzyme- catalyzing few important reactions. • Most abundantly found protein in the world. • Mainly helps in carbon fixation - atmospheric CO2 energy rich molecules like glucose. • Respiration - process of energy release by the breakdown of substrate material.
  4. 4. RuBisCo The enzyme has eight large subunits (blue) and eight small ones (gray), tightly packed into a structure
  5. 5. RuBisCo • Contains two types of protein subunits-Large Chain & Small Chain. A total of 8 large chains & 8 small chains assemble to form a large complex of about. • Large Chain gene (rbcL) - part of Chloroplast DNA & Small Chain genes - associated with plant cell DNA. • Active site of this enzyme is on Large Chain.
  6. 6. Activation of RuBisCo RuBisCo RuBisCo Lys (NH3+) Lys NH2 Lys NH Coo- CO2 H+ RuBisCo Lys NH COO- Mg2+ ACTIVE COMPLEX RuBisCo H+ Mg2+
  7. 7. Functions • Dual role-Carboxylation of RUDP & Oxygenase Activity.
  8. 8. Photorespiration • Respiration-Process of energy release by the breakdown of substrate material. • In plants respiration is seen in dark as well as in light. Phenomenon of consumption of oxygen and release of carbon-di-oxide in the presence of light—Photorespiration.
  9. 9. Photorespiration Site of Photorespiration:  Normal respiration in cytosol and Mitochondria. Here it occurs in three organelles with coordination- Chloroplast, Peroxisomes & Mitochondria.
  10. 10. Photorespiration Conditions for Photorespiration: Light Temperature—25-35⁰C Oxygen-High concentration CO2-Low Concentration.
  11. 11. Photorespiration MECHANISM: In Chloroplast— 2-Phosphoglycolic acid 2-Phosphoglycolic acid Glycolic Acid RuBisCo Phosphatase RUDP + O2 + H2O
  12. 12. H2O2 2H2O + O2 Glycolic acid Glyoxylic acid Catalase G.A.oxidase + H2O2+ O2 In Peroxisomes
  13. 13. Glyoxylic acid Glutamic Acid Glycine α-Ketoglutaric acid Glyoxalate Amino transferase+ +
  14. 14. • In Mitochondria Glycine Serine Dehydrogenase Decarboxylase 2mols +H2O+NAD CO2+NH3+NADH2 +
  15. 15. • In Peroxisomes Hydroxy pyruvic acid Glycine Glyoxylic amino transferase Glyoxylic acid Serine + +
  16. 16. Hydroxy pyruvic acid Glyceric Acid + NAD Hydroxy pyruvate reductase
  17. 17. • In Chloroplast PGA Glyceric acid kinase Glyceric Acid + ATP This PGA-joins with PGA of Calvin’s cycle –synthesis of carbohydrates.
  18. 18. Conclusion • From the above discussion we conclude that RuBisCo is a very important enzyme in plants for energy production. • Some uses of photorespiration are: Removes toxic metabolic intermediates Protects from photoinhibition.
  19. 19. Reference •Lehninger, Principles of Biochemistry 5th edition; David.L.Nelson & Micheal.M.Cox, W. H. Freeman and Company,41 Madison Avenue, New York, NY 10010,Houndmills, Basingstoke RG21 6XS, England. •www.ehow.com •www.ebi.ac.uk
  20. 20. Acknowledgement Sincere thanks to my guide Ragi Jadimurthy for guiding me in this seminar and Dr. NS Devaki for providing me this opportunity. Thank you all for your patient listening.

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