The ATPase activity of phosphorylase kinase is regulated in parallel with its protein kinase activity

• Published in: The Journal of biological chemistry Vol. 266; no. 25; pp. 16524 - 16529
• Main Authors: PAUDEL, H. K, CARLSON, G. M
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 05-09-1991
• Subjects: Adenosine Diphosphate - metabolism; Adenosine Triphosphatases - metabolism; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Calcium - metabolism; Egtazic Acid; Enzyme Activation; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Glycerophosphates - metabolism; Kinetics; Phosphorylase Kinase - metabolism; Phosphorylation; Protein Conformation; Protein Kinases - metabolism; Rabbits; Transferases; Regulation(control); Enzymatic activity; Enzyme; Protein kinase; Enzymatic digestion; Kinetics; Phosphorylase kinase
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)55332-1

Phosphorylase kinase from rabbit skeletal muscle has been found to have an intrinsic ATPase activity that occurs at a rate
approximately 0.2% of that of its phosphorylase conversion activity and about three times that of its autophosphorylation
activity. The characteristics of this ATPase activity were in all aspects tested essentially the same as the kinase's phosphorylase
conversion activity. The ATPase requires Mg2+ and is dramatically stimulated by Ca2+ ions. At neutral pH there is a pronounced
lag in the rate of product formation that is not present at alkaline pH, a condition that greatly stimulates both the phosphorylase
conversion and ATPase activities. ATP is preferentially hydrolyzed over GTP and the Km for MgATP determined in the ATPase
assay is 0.14 mM. ADP, an allosteric activator of phosphorylase conversion, also stimulates the ATPase activity, whereas beta-glycerophosphate,
an inhibitor of phosphorylase conversion, is an inhibitor of the ATPase activity. Phosphorylation or partial proteolysis of
the kinase, which are known to activate phosphorylase conversion, also activate the ATPase activity. Because the phosphorylase
conversion and ATPase activities are regulated in parallel, we conclude that activation of the two catalytic activities must
share a common underlying basis, namely an enhanced phosphotransferase activity that is independent of the phosphoryl acceptor.