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  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. • •
  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.