glyoxylate cycle


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glyoxylate cycle

a modification of the KREBS CYCLE which is found in higher plants (particularly germinating seeds) and some microorganisms, enabling them to grow on acetate or other compounds that yield ACETYL COA. The cycle involves certain reactions of the Krebs cycle, but bypasses the two decarboxylation reactions. Oxaloacetate condenses with acetyl CoA to form citrate, which isomerizes to isocitrate. Isocitrate lyase is then involved in cleaving isocitrate into succinate and glyoxylate. Acetyl CoA condenses with glyoxylate to form malate catalysed by malate synthase, and malate is oxidized to oxaloacetate. Two molecules of acetyl CoA enter per turn of the glyoxylate cycle compared with one in the Krebs cycle. In plants the glyoxylate cycle takes place in organelles called GLYOXYSOMES.