Glyoxysome

Role Of Glyoxysome In Glyoxylate Cycle

1. Role Of Glyoxysome In Glyoxylate Cyclic Presented By Hina Tabassum (7519) Maryam Riasat (7545) BS Zoology (5 th Semester – Morning)

2. Glyoxysome

3. Introduction:- Micro-Bodies S pecialized form of peroxisome Present in plant cells (Germinating seeds) Not found in animal cells except some lower animals (Nematodes )

4. Contain the enzymes of the Glyoxylate Cycle Enzymes Citrate synthase, isocitrate lyase, malate synthase etc   They contain all the enzymes necessary for fatty acid oxidation in G lyoxylate C ycle and Gluconeogenesis .

5. Discovery :- R.W Breidenbach and H. Beevers In 1961 Microbodies of the fat-storing cells of germi­nating seeds contain enzymes Enzyme were found in the organelle other than mitochondria (Glyoxysomes)

6. Role Of Glyoxysomes In Glyoxylate Cycle Main Aim:- Convert acetyl C oA into succinate for the synthesis of carbohydrates . Fatty acid → Carbohydrates In M icroorganisms in the absence of glucose this cycle allows cells to utilize carbon compounds as a carbon source.

7. Absent in lipid-poor seed such as the pea

8. Role In Glyoxylate Cyclic Present in plants e.g (Oil rich seeds) Soya beans, Castor beans, Sunflower beans

9. Present at the time of Germination (Plant seedling) Removed in living plants when they become able to produce their own food from photosynthesis Energy comes from the stored fatty acids Fatty acid → Carbohydrates Glyoxysomes undergo catabolism & anabolism of lipids

10. Catabolism carried by the enzymes present in glyoxysomes (Glyoxylate Cycle) Contain material to begin formation of new plants Form epicotyl & hypocotyl

11. Temporary structures When body sustain itself (roots & shoots are developed) they are removed Seeds → Germination → Plant body

12. Enzymes involve in Glyoxylate Cycle The   glyoxylate cycle  utilizes five   enzymes that are following:- Citrate synthase Aconitase Isocitrate lyase Malate synthase Malate dehydrogenase

13. Glyoxylate Cycle

14. Steps Involved In Glyoxylate Cycle:- Various steps of this cycle are as follows:- Acetyl-CoA produced after the β-oxidation of fatty acids condenses with oxaloacetic acid to form Citric Acid.

15. Citric acid is dehydrated to produce Cis-aconitic Acid in the presence of Aconitase .

16. Cis-aconitic acid reacts with one molecule of H 2 O to form Iso-citric acid .

17. Iso-citric acid is broken down into glyoxylic acid and succinic acid by the enzyme Isocitratase .

18. Glyoxylic acid combines with acetyl CoA (produced after the β-oxidation of fatty ac­ids) in the presence of Malate synthetase to produce Malic acid.

19. Malic acid is oxidised into oxaloacetic acid in the presence of Malic dehydrogenase and the coenzyme NAD . Oxaloacetic acid thus produced combines with acetyl-CoA to regenerate citric acid.

20. Role Of Glyoxylate Cycle In Pathogenic Fungi Main enzymes Iso c itrate Lyase and malate synthase are increased upon contact with the human host. Mutant of particular fungi that lacked Isocitrate Lyase are less virulant. Glyoxylate Cycle is a significant factor for the pathogenesis of these microbes.

21. Role Of Glyoxylate Cycle In Gluco-neo-genesis Fatty acid from lipids are used as an energy source. Fatty acid is converted into acetate molecule by beta oxidation. Acetate +active thiol group (coenzyme A) > TCA cycle > CO2 This pathway allows cells to obtain energy from fats.