title: [Regulatory properties of phosphorylase from chicken skeletal muscle].
abstract: The main kinetic parameters for purified phosphorylase kinase from chicken skeletal muscle were determined at pH 8.2: Vm = 18 micromol/min/mg; apparent Km values for ATP and phosphorylase b from rabbit muscle were 0.20 and 0.02 mM, respectively. The activity ratio at pH 6.8/8.2 was 0.1-0.4 for different preparations of phosphorylase kinase. Similar to the rabbit enzyme, chicken phosphorylase kinase had an absolute requirement for Ca2+ as demonstrated by complete inhibition in the presence of EGTA. Half-maximal activation occurred at [Ca2+] = 0.4 microM at pH 7.0. In the presence of Ca2+, the chicken enzyme from white and red muscles was activated 2-4-fold by saturating concentrations of calmodulin and troponin C. The C0.5 value for calmodulin and troponin C at pH 6.8 was 2 and 100 nM, respectively. Similar to rabbit phosphorylase kinase, the chicken enzyme was stimulated about 3-6-fold by glycogen at pH 6.8 and 8.2 with half-maximal stimulation occurring at about 0.15% glycogen. Protamine caused 60% inhibition of chicken phosphorylase kinase at 0.8 mg/ml. ADP (3 mM) at 0.05 mM ATP caused 85% inhibition with Ki = 0.2 mM. Unlike rabbit phosphorylase kinase, no phosphorylation of the chicken enzyme occurred in the presence of the catalytic subunit of cAMP-dependent protein kinase. Incubation with trypsin caused 2-fold activation of the chicken enzyme.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology; D002645:Chickens; D004789:Enzyme Activation / Q000187:drug effects; D006003:Glycogen / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D009132:Muscles / Q000201:enzymology*; D010764:Phosphorylase Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D011479:Protamines / Q000494:pharmacology; D014336:Troponin / Q000494:pharmacology; D019209:Troponin C
chemical_list: D002147:Calmodulin; D011479:Protamines; D014336:Troponin; D019209:Troponin C; D000244:Adenosine Diphosphate; D006003:Glycogen; D010764:Phosphorylase Kinase; D002118:Calcium
vernacular_title: Reguliatornye svoĭstva fosforilazy iz skeletnykh myshts kuritsy.