Figure 1

Overall reaction scheme and crystal structure of AMP bound AC. (a) Reaction of ACs. The sequential phosphorylation of the products acetone and then bicarbonate by the γ then β phosphates from ATP, respectively, creates the highly reactive intermediates phosphoenolacetone and carboxyphosphate. These are proposed to react together at the Mn²⁺ active site to create acetoacetate and two molecules of inorganic phosphate (Pi). (b) The overall structure of the (αβγ)₂ heterohexameric AC enzyme is shown: α subunits (green), β subunits (blue), γ subunits (violet). One monomer is transparent to indicate the dimer interface as well as the nucleotide binding site. Mn²⁺, Zn²⁺ and AMP binding sites are indicated with arrows.