Effect of free Mg2+ on liver phosphorylase kinase activity.
When pig liver phosphorylase kinase was assayed at various concentrations of Mg2+, about 2-fold stimulation was observed around 2-3 mM Mg2+ (Mg2+/ATP ratio, 20-30) compared with the activity at 0.3 mM Mg2+ (Mg2+/ATP ratio, 3). This stimulation was specific for Mg2+ among the divalent cations tested and the process was reversible. Km values for ATP and phosphorylase b were decreased 3.6- and 9.5-fold, respectively, at 3 mM Mg2+ compared with those obtained at 0.3 mM Mg2+. These results indicate that the activity of liver phosphorylase kinase is influenced by free Mg2+.
D000818:Animals; D002413:Cations, Divalent; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology*; D010764:Phosphorylase Kinase / Q000378:metabolism*; D010763:Phosphorylase b / Q000378:metabolism; D013552:Swine
D002413:Cations, Divalent; D010763:Phosphorylase b; D010764:Phosphorylase Kinase; D008274:Magnesium