Catalyzes the dehydration of 2-methylcitrate (2-MC) to yield the cis isomer 2-methyl-aconitate. (2S,3S)-2-methylcitrate = 2-methyl-cis-aconitate + H2O Monomer. The prpD1B1C1 operon seems not to be involved in propionate degradation. Belongs to the PrpD family.