Involved in the metabolic adaptation in response to environmental changes. Catalyzes the reversible formation of succinate and glyoxylate from isocitrate, a key step of the glyoxylate cycle, which operates as an anaplerotic route for replenishing the tricarboxylic acid cycle during growth on fatty acid substrates. D-threo-isocitrate = glyoxylate + succinate Divalent metal cations. Can also use Mn(2+) ion. Activated by phosphorylation on histidine. Competitively inhibited by 3-phosphosglycerate, oxalate, malate, chloride, phosphate and sulfate ions, and uncompetitively inhibited by succinate and phosphoenolpyruvate (PEP). kcat is 28.5 sec(-1) for isocitrate lyase activity with threo-D-isocitrate as substrate (at pH 7.3). Optimum pH is 7.3. Carbohydrate metabolism; glyoxylate cycle; (S)-malate from isocitrate: step 1/2. Homotetramer. Belongs to the isocitrate lyase/PEP mutase superfamily. Isocitrate lyase family.