Involved in the catabolism of short chain fatty acids (SCFA) via the 2-methylcitrate cycle I (propionate degradation route). Catalyzes the dehydration of 2-methylcitrate (2-MC) to yield the cis isomer of 2-methyl-aconitate. It is also able to catalyze the dehydration of citrate at a lower rate, and the hydration of cis-aconitate. It has no aconitase-like activity and is unable to catalyze the hydration of 2-methyl-cis-aconitate. (2S,3S)-2-methylcitrate = 2-methyl-cis-aconitate + H2O citrate = D-threo-isocitrate Organic acid metabolism; propanoate degradation. Carbohydrate metabolism; tricarboxylic acid cycle; isocitrate from oxaloacetate: step 2/2. Monomer. Cells lacking this gene accumulate 2-methylcitrate during growth on propionate. Belongs to the PrpD family.