Characterization of the major phosphofructokinase - dephosphorylating protein phosphatases from Ascaris suum muscle

Guenter Daum, Brigitte Schmid, Carol MacKintosh, Philip Cohen, H. Werner Hofer

    Research output: Contribution to journalArticlepeer-review

    6 Citations (Scopus)


    In contrast to the mammalian enzyme, PFK from the nematode Ascaris suum is activated following phosphorylation (Daum et al. (1986) Biochem. Biophys. Res. Commun. 139, 215-221) catalyzed by a cAMP-dependent protein kinase (Thalhofer et al. (1988) J. Biol. Chem. 263, 952-957). In the present report, we describe the characterization of the major PFK dephosphorylating phosphatases from Ascaris muscle. Two of these phosphatases exhibit apparent M(r) values of 174 000 and 126 000, respectively, and are dissociated to active 33 kDa proteins by ethanol precipitation. Denaturing electrophoresis of each of the enzyme preparations showed two bands of M(r) 33 000 and 63 000. The enzymes are classified as type 2A phosphatases according to their inhibition by subnanomolar concentrations of okadaic acid, the lack of inhibition by heat-stable phosphatase inhibitors 1 and 2, and their preference for the alpha- rather than for the beta-subunit of phosphorylase kinase. Like other type 2A phosphatases, they exhibit broad substrate specificities, are activated by divalent cations and polycations, and inhibited by fluoride, inorganic phosphate and adenine nucleotides. In addition, we have found that PFK is also dephosphorylated by an unusual protein phosphatase. This exhibits kinetic properties similar to type 2A protein phosphatases, but has a distinctly lower sensitivity towards inhibition by okadaic acid (IC50 approx. 20 nM). Partial purification of the enzyme provided evidence that it is composed of a 30 kDa catalytic subunit and probably two other subunits (molecular masses 66 and 72 kDa). The dephosphorylation of PFK by protein phosphatases is strongly inhibited by heparin. This effect, however, is substrate-specific and does not occur with Ascaris phosphorylase a.

    Original languageEnglish
    Pages (from-to)23-32
    Number of pages10
    JournalBiochimica et Biophysica Acta. Protein Structure and Molecular Enzymology
    Issue number1
    Publication statusPublished - 1992


    Dive into the research topics of 'Characterization of the major phosphofructokinase - dephosphorylating protein phosphatases from Ascaris suum muscle'. Together they form a unique fingerprint.

    Cite this