Catalyzes the carboxylation of acetone to form acetoacetate. Has a reduced activity on butanone, and no activity on 2-pentatone, 3-pentatone, 2-hexanone, chloroacetone, pyruvate, phosphoenolpyruvate, acetaldehyde, propionaldehyde and propylene oxide. acetone + 2 ATP + 3 H2O + hydrogencarbonate = acetoacetate + 2 AMP + 4 H(+) + 4 phosphate Zn(2+). The heterohexamer contains tightly bound iron, manganese and zinc ions. Optimum pH is 7.6. Heterohexamer of two alpha, two beta and two gamma subunits.