Download - PHOTORESPIRATION
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RuBisCo & ITS ROLE IN
PHOTORESPIRATION
By-Narayan Prahlad.VV Semester Mol.Bio
9/9/2014
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Contents
Introduction RuBisCo Activation of RuBisCo Function Photorespiration Conclusion Reference Acknowledgement
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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.
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RuBisCo
The enzyme has eight large subunits (blue) and eight small ones (gray), tightly packed into a structure
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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.
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Activation of RuBisCo
RuBisCo RuBisCo Lys (NH3+) Lys
NH2 Lys NH
Coo-
CO2H+
RuBisCo Lys NH COO-Mg2+
ACTIVE COMPLEX
RuBisCoH+
Mg2+
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Functions
• Dual role-Carboxylation of RUDP & Oxygenase Activity.
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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.
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Photorespiration
Site of Photorespiration: Normal respiration in cytosol and
Mitochondria.
Here it occurs in three organelles with coordination- Chloroplast, Peroxisomes & Mitochondria.
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Photorespiration
Conditions for Photorespiration:LightTemperature—25-35⁰COxygen-High concentrationCO2-Low Concentration.
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Photorespiration
MECHANISM: In Chloroplast—
2-Phosphoglycolic acid
2-Phosphoglycolic acid Glycolic Acid
RuBisCo
Phosphatase
RUDP + O2
+ H2O
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H2O2 2H2O + O2
Glycolic acid Glyoxylic acid
Catalase
G.A.oxidase + H2O2+ O2
In Peroxisomes
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Glyoxylic acid Glutamic AcidGlycine
α-Ketoglutaric acid
GlyoxalateAmino transferase+
+
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• In Mitochondria
Glycine Serine
Dehydrogenase
Decarboxylase 2mols +H2O+NAD
CO2+NH3+NADH2
+
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• In Peroxisomes
Hydroxy pyruvic acid
Glycine
Glyoxylic amino transferase
Glyoxylic acid Serine+
+
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Hydroxy pyruvic acidGlyceric Acid
+ NADHydroxy pyruvate reductase
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• In Chloroplast
PGA
Glyceric acid kinase
Glyceric Acid
+ ATP
This PGA-joins with PGA of Calvin’s cycle –synthesis of carbohydrates.
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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 intermediatesProtects from photoinhibition.
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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
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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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