The glyoxylate cycle is an alternative pathway to the citric acid cycle that allows organisms like plants and bacteria to use fatty acids and other two-carbon compounds as their sole carbon source. The cycle bypasses the decarboxylation steps of the citric acid cycle to ensure the two carbons of each acetyl-CoA are retained. This allows the conversion of acetyl-CoA into four-carbon succinate that can then be used to generate carbohydrates like glucose. The glyoxylate cycle occurs in specialized organelles called glyoxysomes in plants and helps the conversion of stored lipids into carbohydrates during seed germination.

1. GLYOXYLATE CYCLE
Submitted by:-
Sonal Singh
(18BMIN001)
Department of Microbiology
Submitted to:-
Ms. Devki
Department of Microbiology

2. INTRODUCTION
• The Glyoxylate cycle is a sequence of anaplerotic
reactions (reactions that form metabolic
intermediates for biosynthesis) that enables an
organism to use substrates that enter central
carbon metabolism at the level of Acetyl Co-A as
the sole carbon source.
• Such substrates include fatty acids, alcohols, and
esters (often the products of fermentation), as
well as waxes, alkenes, and methylated
compounds.
• The pathway does not occur in vertebrates, but it
is found in plants and certain bacteria, fungi, and
invertebrates.

3. HISTORY
• The pathway was originally discovered in
bacteria [Kornberg,57], but later was found to
operate in some eukaryotic organisms as well.
• In plants, the cycle is involved in the
metabolism of storage oils during germination
of seeds [Brownleader,97].
• The cycle also operates in developing eggs of
nematodes, where it converts triacylglycerols
to carbohydrates [Patel,78].

4. What is GLYOXYLATE CYCLE?
• The plants and many microorganisms are
equipped with the metabolic machinery which
converts the fat into carbohydrates.
• It is a cyclic pathway in which 2 Acetyl Co-A
are converted into 1 molecule of Succinate.
• But not in animals, since they cannot carry out
the net synthesis of carbohydrates from fat.

5. • LOCATION :- It occurs in many bacterias,
plants, protists, and fungi.
• In plants, it occurs in the glyoxysomes, which
is a specialized peroxisome that carries out β-
oxidation of that Acetyl Co-A in the Glyoxylate
cycle.
• Human pathogen such as Mycobacterium
tuberculosis, uses Glyoxylate cycle to convert
lipids into carbohydrates.

6. REACTION
• The Glyoxylate cycle is an anabolic variant of
the Citric Acid cycle.
• Acetyl Co-A produced from fatty acid
oxidation condenses with Oxaloacetate to
give Citrate.
• Citrate is then converted to Isocitrate.
• Here, Isocitrate bypasses the TCA cycle and
cleave by Isocitratelyase to Succinate and
Glyoxylate.

8. • Another molecule of Acetyl Co-A is now
utilized to combine with Glyoxylate to form
Malate. This reaction is catalysed by Malate
synthase.
• Finally, Malate dehydrogenase oxidises Malate
to Oxaloacetate and enters TCA cycle.
• It results in the conversion of two 2-C
fragments of Acetyl Co-A to 4-C compound,
Succinate.

9. • The Succinate produced within the
glyoxysome is transferred to the
mitochondria, where it enters TCA cycle and is
converted to Malate, which has 2 fates:-
i. It can be converted to Oxaloacetate in
mitochondria continuing TCA cycle.
ii. It can be transported to cytosol where it is
converted to Oxaloacetate for entry into
Gluconeogenesis.
• Bypass reaction= α- Ketoglutarate, Succinyl
Co-A.

10. THANK YOU !!!