Reversible inhibition of skeletal muscle phosphoprotein phosphatase by ATP, phosphate and fluoride

Balwant S. Khatra, Thomas R. Soderling

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    42 Scopus citations


    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 languageEnglish (US)
    Pages (from-to)647-654
    Number of pages8
    JournalBiochemical and Biophysical Research Communications
    Issue number2
    StatePublished - Nov 29 1978


    ASJC Scopus subject areas

    • Biophysics
    • Biochemistry
    • Molecular Biology
    • Cell Biology

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