ackA

AckA, or acetate kinase A, is a bacterial enzyme encoded by the ackA gene. It functions in the metabolism of acetate by catalyzing the reversible transfer of a phosphate between acetyl phosphate and ADP/ATP: acetyl phosphate + ADP ⇌ acetate + ATP. In many bacteria, AckA works together with phosphotransacetylase (Pta) in the phosphotransacetylase- acetate kinase (Pta-AckA) pathway, which links acetyl-CoA metabolism to energy production. When acetyl phosphate is converted to acetate, ATP is generated from ADP, providing substrate-level phosphorylation during fermentative growth. The reaction is reversible and can operate in the opposite direction under different cellular conditions, allowing acetyl phosphate formation from acetate and ATP.

Genetically, ackA is widespread among bacteria and is frequently co-located with pta in an operon in organisms such as Escherichia coli. This operon arrangement reflects the functional link between acetyl-CoA metabolism, acetyl phosphate, and acetate production. Expression of ackA (and pta) is influenced by the carbon source and growth conditions, with acetyl phosphate levels contributing to regulatory effects on certain two-component signaling systems.

Biochemical and cellular context: AckA belongs to the ASKHA superfamily of kinases and is typically a cytosolic enzyme requiring divalent metal ions such as Mg2+. Beyond metabolism, acetyl phosphate can serve as a high-energy phosphoryl donor for response regulators in signaling pathways, linking metabolic state to gene regulation in some bacteria.

See also: pta, acetyl-CoA, acetyl phosphate, two-component systems.