Phosphorylated Acetate Kinase

Acetate kinase (ATP:acetate phosphotransferase, EC 2.7.2.1) can be phosphorylated with ATP or with acetyl phosphate. The degree of phosphorylation increases with the relative concentration of phosphorylating agent. The isolated phosphoenzyme reacts quantitatively with ADP to form ATP, and with acetate to form acetyl phosphate in 70 to 80% yield. The pH stability profile of the phosphoenzyme at 37° has a U shape characteristic of acyl phosphates. Neutral hydroxylamine at 26° reacts rapidly (10 min) with the phosphoenzyme to effect the quantitative release of orthophosphate. These properties intimate that the phosphoryl group of the phosphoenzyme is linked covalently to a carboxyl function of the enzyme.