title: Novel heparin-activated protein kinase activity in rabbit skeletal muscle.
abstract: 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, half-maximally at 3 micrograms/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 micrograms/ml. The heparin-activated protein kinase is clearly distinguishable from other known glycogen synthase kinases.
mesh_terms: D000818:Animals; D004789:Enzyme Activation; D006493:Heparin / Q000494:pharmacology*; D007700:Kinetics; D046911:Macromolecular Substances; D009132:Muscles / Q000201:enzymology*; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits
chemical_list: D046911:Macromolecular Substances; D006493:Heparin; D011494:Protein Kinases