Involved in the ethylmalonyl-CoA pathway for acetate assimilation. Catalyzes the reversible condensation of glyoxylate and acetyl-CoA to L-malyl-CoA and the reversible condensation of glyoxylate and propionyl-CoA to yield beta-methylmalyl-CoA (By similarity). (S)-malyl-CoA = acetyl-CoA + glyoxylate (2R,3S)-beta-methylmalyl-CoA = glyoxylate + propanoyl-CoA Divalent cations such as magnesium or manganese. Homohexamer. Dimer of trimers (By similarity). Belongs to the HpcH/HpaI aldolase family.