Figure 4

Phosphorylation of substrates. The phosphorylation reaction takes place in the β-subunit nucleotide-binding site. The phosphorylation of acetone starts with deprotonation of α-carbon of acetone by a yet unidentified basic residue, forming an enolate which is phosphorylated by the γ-phosphate (blue) to form phosphoenolacetone. Bicarbonate is subsequently phosphorylated by the β-phosphate (green) to form carboxyphosphate and AMP.