Kinetic mechanisms of Ca ++/calmodulin dependent protein kinases

• Published in: Archives of biochemistry and biophysics 2011-02, Vol.506 (2), p.130-136
• Main Authors: Huynh, Q. Khai, Pagratis, Nikos
• Format: Article
• Language: English
• Subjects: adenosine diphosphate; Adenosine Diphosphate - metabolism; Adenosine Diphosphate - pharmacology; adenosine triphosphate; Adenosine Triphosphate - metabolism; calcium; Calcium-Binding Proteins - metabolism; Calcium-Binding Proteins - pharmacology; Calcium-Calmodulin-Dependent Protein Kinase Type 1 - antagonists & inhibitors; Calcium-Calmodulin-Dependent Protein Kinase Type 1 - chemistry; Calcium-Calmodulin-Dependent Protein Kinase Type 1 - metabolism; Calcium-Calmodulin-Dependent Protein Kinase Type 2 - antagonists & inhibitors; Calcium-Calmodulin-Dependent Protein Kinase Type 2 - chemistry; Calcium-Calmodulin-Dependent Protein Kinase Type 2 - metabolism; Calcium-Calmodulin-Dependent Protein Kinase Type 4 - antagonists & inhibitors; Calcium-Calmodulin-Dependent Protein Kinase Type 4 - chemistry; Calcium-Calmodulin-Dependent Protein Kinase Type 4 - metabolism; Calcium-Calmodulin-Dependent Protein Kinases - antagonists & inhibitors; Calcium-Calmodulin-Dependent Protein Kinases - chemistry; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Calmodulin; CaMK; dissociation; Humans; In Vitro Techniques; isozymes; Kinetic mechanism; Kinetics; Phospholamban; protein kinases; reaction mechanisms; Recombinant Proteins - antagonists & inhibitors; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Substrate Specificity
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/j.abb.2010.11.008

► Kinetic analysis of CaMK family indicated that their reaction mechanisms were of the sequential type in which all substrates must bind to enzyme before any product is released. ► While CaMK I and CaMK IV exhibited random sequential mechanism where either phospholamban or ATP can bind to the free enzyme; CaMK IIs exhibited Ordered Bi Bi mechanism in which phospholamban is the first substrate to bind. ► Constant a of all isozymes for ATP and peptide was higher than 1 indicating that the binding of phospholamban to CaMK decreased the enzyme’s affinity toward ATP. Many of the cellular responses to Ca ++ signaling are modulated by a family of multifunctional Ca ++/calmodulin dependent protein kinases (CaMKs): CaMK I, CaMK II and CaMK IV. In order to further understand the role of CaMKs, we investigated the kinetic mechanism of CaMK II isozymes in comparison with those of CaMK I and CaMK IV by analyzing their steady state kinetics using phospholamban as a phosphoacceptor. The results indicated that (a) the CaMK family’s reaction mechanisms were of the sequential type in which all substrates must bind to enzyme before any product is released; (b) CaMK I and CaMK IV exhibited random sequential mechanism where either phospholamban or ATP can bind to the free enzyme; (c) the data of product inhibition for CaMK IIs best fit with an Ordered Bi Bi mechanism in which phospholamban is the first substrate to bind and ADP is the last product to be released; and (d) the constant α (ratio of apparent dissociation constants for binding peptide in the presence and absence of the second ligand) of all isozymes for ATP and peptide was higher than 1 indicating that the binding of phospholamban to CaMK decreased the enzyme’s affinity toward ATP.