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 Homotetramer; dimer of dimers. The prpD1B1C1 operon seems not to be involved in propionate degradation. Belongs to the isocitrate lyase/PEP mutase superfamily. Methylisocitrate lyase family. Truncated N-terminus.