On the Mechanism of Activation of Phosphorylase b Kinase by Calcium

• Published in: The Journal of biological chemistry Vol. 243; no. 21; pp. 5532 - 5538
• Main Authors: Drummond, G I, Duncan, L
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 10.11.1968
• Subjects: Animals; Brain - enzymology; Brain Chemistry; Calcium; Cattle; Chemical Precipitation; Chromatography, Gel; Chromatography, Ion Exchange; Electrophoresis; Muscle Proteins - isolation & purification; Myocardium; Nerve Tissue Proteins - isolation & purification; Peptide Hydrolases; Phosphorylase Kinase - antagonists & inhibitors; Protease Inhibitors; Rabbits; Ultracentrifugation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(18)91901-0

Kinase-activating factor, a protein required for the activation of phosphorylase b kinase by Ca ++ , was purified from brain tissue and from skeletal muscle and myocardium. All fractions contained calcium-activated proteinase activity as measured by the formation of acid-soluble, tyrosine-positive material with casein as substrate. The ratio of kinase-activating factor activity to proteinase activity remained constant throughout the purification, and both activities coincided on Sephadex G-100 filtration. Kinase-inhibitory factor, which prevents activation of kinase by Ca ++ , inhibited proteinase activity. Kinase-inhibitory factor also prevented the activation of kinase by trypsin. Acid-soluble, ninhydrin-positive material was formed during the activation of phosphorylase kinase by kinase-activating factor in the presence of Ca ++ . It is concluded that kinase-activating factor is a calcium-activated proteolytic enzyme, that kinase-inhibitory factor is a proteolytic inhibitor, and that activation of phosphorylase b kinase by Ca ++ involves proteolysis.