Catalyzes the carboxylation of acetophenone to form 3-oxo-3-phenylpropanoate (benzoylacetate) in the anaerobic catabolism of ethylbenzene. Also carboxylates propiophenone at the same rate and 4-acetyl-pyridine at lower rates. acetophenone + 2 ATP + H2O + hydrogencarbonate = 3-oxo-3-phenylpropanoate + 2 ADP + 2 H(+) + 2 phosphate Divalent metal cations. Magnesium or manganese are required for activity. Inhibited by zinc ions, carbamoylphosphate and beta,gamma-imido-ATP. Kinetic parameters have been established using the heteromeric complex including recombinant Apc5. Acetophenone carboxylase consists of five subunits; a heterooctameric subcomplex of two alpha (Apc1), two beta (Apc2), two gamma (Apc3) and two delta (Apc4) subunits assembles with the epsilon (Apc5) subunit in an unknown stoichiometry. By ethylbenzene, toluene and acetophenone. The epsilon subunit dissociates during enzyme purification. However, Apc5 is required for acetophenone carboxylation and the enzyme complex is reconstituted using recombinant Apc5.