Glyoxylate cycle for UG students

1. Niranjana M.R.
Assistant Professor
Sree Krishna College
Guruvayoor

2.  In fatty seeds - to convert Acetyl CoA to Glucose
 During germination.
 Acetyl CoA- Beta oxidation of fatty acids
 Why not the reversal of Glycolysis??
-because, conversion of PEP to Pyruvate and
Pyruvate to Acetyl CoA is so exergonic-
IRREVERSIBLE
 Seen in all organisms except vertebrates- Plants
and yeast mainly.
 Occurs in Glyoxisomes- specialised peroxisomes

4.  2 acetyl CoA + NAD+ + 2H2OSuccinate+2CoA+
NADH+H+
Succinate enters gluconeogenesis-
Glucose for seedling development
5 reactions- 5 enzymes-membrane
bound
2 key enzymes;
 ISOCITRATE LYASE
 MALATE SYNTHASE

5. Acetyl CoA condenses with Oxaloacetate
Citrate- TCA cycle reaction- Isozymes
Citrate synthase
AcetylCoA+ OAA Citrate

6. Citrate is converted to Isocitrate
Aconitase
Intramolecular rearrangement- TCA cycle
rxn
Citrate- Isocitrate

7. Isocitrate cleaved to GLYOXYLATE and
SUCCINATE.
ISOCITRATE LYASE
Isocitrate
Glyoxylate+Succinate
GLUCONEOGENESIS

8. Glyoxylate condenses with second acetyl
CoA
Malate
MALATE SYNTHASE
Glyoxylate+ Acetyl CoA
Malate

9. Malate oxidised to Oxaloacetate
Malate Dehydrogenase
NADH+H+ formed
Malate Oxaloacetate