Catalyzes the formation of (2S,5S)-carboxymethylproline (t-CMP) from malonyl-CoA and (S)-1-pyrroline-5-carboxylate, the first step in the biosynthesis of (5R)-carbapen-2-em-3-carboxylate, a beta-lactam antibiotic of the carbapenem class (PubMed:15595850, PubMed:14625287). Also catalyzes the independent decarboxylation of malonyl-CoA and methylmalonyl-CoA and the hydrolysis of CoA esters such as acetyl-CoA and propionyl-CoA (PubMed:15595850). Catalyzes the reaction with a C2 epimeric mixture of methylmalonyl-CoA to give a 55:45 mixture of (6R)- and (6S)-epimers of 6-methyl-t-CMP, under standard incubation conditions (PubMed:21505494). (S)-1-pyrroline-5-carboxylate + H(+) + H2O + malonyl-CoA = (2S,5S)-5-carboxymethylproline + CO2 + CoA kcat is 1.7 sec(-1) with malonyl-CoA as substrate. kcat is 1.52 sec(-1) with (S)-1-pyrroline-5-carboxylate as substrate. Antibiotic biosynthesis; carbapenem biosynthesis. Homotrimer. Unusual member of the enoyl-CoA hydratase/isomerase family: in addition to decarboxylation and thioester hydrolysis steps, catalyzes C-C bond formation leading to a substituted heterocycle. Glu-131 is important in both C-C bond formation and thioester hydrolysis steps while it does not play an essential role in decarboxylation. Belongs to the enoyl-CoA hydratase/isomerase family.