Involved in caffeate respiration, which consists in the reduction of the C-C double bond of caffeate. CarA catalyzes an energy-saving CoA loop for caffeate activation in the steady state of caffeate respiration. It catalyzes the formation of caffeyl-CoA from caffeate with hydrocaffeyl-CoA as the CoA donor via a ping-pong mechanism. In addition to caffeate, the enzyme can utilize 4-coumarate or ferulate as CoA acceptor. Neither acetyl-CoA nor butyryl-CoA served as the CoA donor. (E)-caffeate + hydrocaffeoyl-CoA = (E)-caffeoyl-CoA + 3-(3,4-dihydroxyphenyl)propanoate kcat is 120 sec(-1) for transferase activity with caffeate as substrate. Optimum pH is 7.5. Optimum temperature is 40 degrees Celsius. Homodimer. Induced by cinnamate and sinapate. Belongs to the 3-oxoacid CoA-transferase family.