Novel heparin-activated protein kinase activity in rabbit skeletal muscle

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A heparin-activated protein kinase has been identified in rabbit skeletal muscle. The enzyme, which had a native molecular mass of 70 kDa as judged by gel filtration, was stimulated 3- to 5-fold by heparin, halfmaximally at 3 μg ml heparin. The stimulation by heparin was not reproduced by other polyanions such as polyaspartate and polyglutamate. The protein kinase was detected by its ability to phosphorylate glycogen synthase; it was ineffective in phosphorylating caseins, phosvitin, histone, or phosphorylase. Glycogen synthase was phosphorylated to a stoichiometry of 0.7-0.8 phosphates/subunit, exclusively at serine residues located in the COOH-terminal CNBr-fragment of the subunit, with a corresponding reduction in the -/+ glucose-6P activity ratio from 0.96 to 0.43. The activity of the protein kinase was unaffected by the presence of Ca2+ and/or phospholipid, cyclic AMP or heat-stable inhibitor protein of cyclic AMP-dependent protein kinase. The enzyme was inhibited about 60% by the presence of glycogen, half-maximal effect at 25 μg ml. The heparin-activated protein kinase is clearly distinguishable from other known glycogen synthase kinases.

Original languageEnglish (US)
Pages (from-to)96-100
Number of pages5
JournalFEBS Letters
Issue number1
StatePublished - Jan 1 1985



  • Heparin Glycogen synthase
  • Protein kinase
  • Rabbit muscle

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology

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