Involved in the catabolism of short chain fatty acids (SCFA) via the 2-methylcitrate cycle I (propionate degradation route). Catalyzes the thermodynamically favored C-C bond cleavage of (2R,3S)-2-methylisocitrate to yield pyruvate and succinate via an alpha-carboxy-carbanion intermediate. (2S,3R)-3-hydroxybutane-1,2,3-tricarboxylate = pyruvate + succinate kcat is 74 sec(-1) for 2-methylisocitrate lyase with 2-methylisocitrate as substrate. Optimum pH is 7.5. Optimum temperature is 50 degrees Celsius. Organic acid metabolism; propanoate degradation. Homotetramer; dimer of dimers. Cells lacking this gene are unable to accumulate 2-methylcitrate and 2-methyl-cis-aconitate. In vitro, dithiothreitol (DTT) or reduced glutathione (GSH) are required for optimal activity. Belongs to the isocitrate lyase/PEP mutase superfamily. Methylisocitrate lyase family.