A phosphoprotein phosphatase preparation which showed activity towards glycogen synthase, phosphorylase, phosphorylase kinase, and phosphohistones was reversibly inhibited (70-90%) by preincubation with free ATP (apparent Ki about 0.3 mM). Other nucleotides (ADP<AMP-P(NH)P<GTP<ATP) and EDTA were only partially effective in inhibiting phosphatase activity. Inhibition was also achieved by preincubation with 50 mM KF or by 16 hr. dialysis against 5 mM potassium phosphate buffer. The inhibition by all these ligands was reversed by a second preincubation with MnCl2 (apparent Ka 3μM) prior to assay. Other divalent metals (Co++ > Zn++ > Mg++) were partially effective in reversing the inhibition. It is concluded that ATP by virtue of its special structure and metal binding capacity possibly removes a catalytically important metal ion from the enzyme.
|Original language||English (US)|
|Number of pages||8|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Nov 29 1978|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology