Involved in the catabolism of short chain fatty acids (SCFA) via the tricarboxylic acid (TCA)(acetyl degradation route) and via the 2-methylcitrate cycle I (propionate degradation route). Catalyzes the Claisen condensation of propionyl-CoA and oxaloacetate (OAA) to yield 2-methylcitrate (2-MC) and CoA. Also catalyzes the condensation of oxaloacetate with acetyl-CoA to yield citrate but with a lower specificity. H2O + oxaloacetate + propanoyl-CoA = (2S,3S)-2-methylcitrate + CoA + H(+) acetyl-CoA + H2O + oxaloacetate = citrate + CoA + H(+) Optimum pH is 9. Optimum temperature is between 45 and 50 degrees Celsius. Organic acid metabolism; propanoate degradation. Carbohydrate metabolism; tricarboxylic acid cycle; isocitrate from oxaloacetate: step 1/2. Homodimer. By propionate, but not acetate or glucose. Expression of prpBCDE operon is regulated by PrpR, CRP and a variety of sugars such as arabinose, galactose, glucose mannose and xylose. Belongs to the citrate synthase family. There is uncertainty concerning the 2-methylcitrate stereochemistry. Brock et al. report a (2S,3S) stereochemistry, but Reddick et al. determined that the 2-methylcitrate has either (2S,3R) or (2R,3S) stereochemistry.