Glyoxylate cycle

The glyoxylate cycle, a variation of the tricarboxylic acid cycle, is an anabolic pathway occurring in plants, bacteria, protists, and fungi. The glyoxylate cycle centers on the conversion of acetyl-CoA to succinate for the synthesis of carbohydrates.

The glyoxylate cycle uses six of the eight enzymes associated with the tricarboxylic acid cycle: citrate synthase, aconitase, succinate dehydrogenase, fumarase, and malate dehydrogenase.

Citrate Synthase

4C oxaloacetate to a 6C molecule citrate

Aconitase

6C Citrate => 6C cis-Aconitate

6C cis-Aconitate => 6C Isocitrate

Succinate Dehydrogenase

Succinate => Fumarate

Fumarase

Fumarate => L-Malate

Malate dehydrogenase

L-Malate => oxaloacetate

The two cycles differ in that in the glyoxylate cycle, isocitrate is converted into glyoxylate and succinate by isocitrate lyase (ICL) instead of into α-ketoglutarate. This bypasses the decarboxylation steps that take place in the citric acid cycle, allowing simple carbon compounds to be used in the later synthesis of macromolecules, including glucose. Glyoxylate is subsequently combined with acetyl-CoA to produce malate, catalyzed by malate synthase. Malate is also formed in parallel from succinate by the action of succinate dehydrogenase and fumarase.

• Malate synthase

MS active site pocket is situated between the TIM barrel and the C-terminal. The ternary complex contains malate, acetyl-CoA and Mg+2 ion^[1].