Glyoxylate cycle isocitrate

The glyoxylate cycle is active in the germinating seeds of some plants and in certain microorganisms that can live on acetate as the sole carbon source. In plants, the pathway takes place in glyoxysomes in seedlings. It involves several citric acid cycle enzymes and two additional enzymes isocitrate lyase and malate synthase. 

The partitioning of isocitrate between the citric acid cycle and the glyoxylate cycle is controlled at the level of isocitrate dehydrogenase, which is regulated by reversible phosphoiylation. 

A key enzyme in the glyoxylate cycle is isocitrate lyase, which cleaves isocitrate (Eq. 13-40) to succinate and glyoxylate. The latter is condensed with a second acetyl group by the action of malate synthase (Eq. 13-38). The L-malate formed in this reaction is dehydrogenated to the regenerating substrate oxalo-... 

An acetyl-CoA-glyoxylate cycle, which catalyzes oxidation of acetyl groups to glyoxylate, can also be constructed from isocitrate lyase and citric acid cycle... 

Partitioning between the Citric Acid and Glyoxylate Cycles In an organism (such as E. coll) that has both the citric acid cycle and the glyoxylate cycle, what determines which of these pathways isocitrate will enter ... 

Figure 17.23 The glyoxylate pathway. The glyoxylate cycle allows plants and some microorganisms to grow on acetate because the cycle bypasses the decarboxylation steps of the citric acid cycle. The reactions of this cycle are the same as those of the citric acid cycle except for the ones catalyzed by isocitrate lyase and malate synthase, which are boxed in blue.

The glyoxylate cycle (Figure 9.13) consists of five reactions. The first two reactions (the synthesis of citrate and isocitrate) are familiar ones, because they also occur in the citric acid cycle. However, the formation of citrate from... 

Plants and some bacteria contain two enzymes (isocitrate lyase and malate synthase) that enable them to synthesize sugars by using the glyoxylate cycle, a variant form of the citric acid cycle. Notice in Figure 14.20 that the glyoxylate cycle uses some of the same enzymes as the citric acid cycle, but that the steps in which decarboxylations occur are bypassed. One of the intermediates in the bypass is glyoxylate, which gives the cycle its name. 

Isocitrate lyase is an enzyme of the glyoxylate cycle that catalyzes the reaction below ... 

D-Isocitrate is a citric acid cycle (and glyoxylate cycle) intermediate produced as a result of action of the enzyme aconitase on citrate. Isocitrate is converted to... 

See also Glyoxylate Cycle, Aconitase, Citrate, Isocitrate Dehydrogenase, ct-Ketoglutarate, Fluorocitrate, Citric Acid Cycle Intermediates, Figure 14.3, Table 14.1... 

Glyoxylate is a two carbon compound generated in the glyoxylate cycle by action of the enzyme isocitrate lyase on isocitrate (the other product of the reaction is succinate). Glyoxylate is combined with acetyl-CoA to form malate by the enzyme malate synthase. 

See also Isocitrate Lyase, Glyoxylate Cycle, Glyoxylate Cycle Intermediates, Figure 14.20, Malate Synthase... 

The glyoxylate cycle (Figure 17.21), like the citric acid cycle, begins with the condensation of acetyl CoA and oxaloacetate to form citrate, which is then isomerized to isocitrate. Instead of being decarboxylated, isocitrate is cleaved by isocitrate lyase into succinate and glyoxylate. The subsequent steps regenerate oxaloacetate from glyoxylate. Acetyl CoA condenses with... 

---