title: Kinetic mechanisms of Ca++/calmodulin dependent protein kinases.
abstract: 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.
authors.affiliation: Research and Development, Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94404, USA. khai.huynh@gilead.com
authors.forename: Q Khai
authors.initials: QK
authors.lastname: Huynh
authors.forename: Nikos
authors.initials: N
authors.lastname: Pagratis
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism / Q000494:pharmacology; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D000099211:Phospholamban
chemical_list: D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D002135:Calcium-Binding Proteins; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D011994:Recombinant Proteins; D000099211:Phospholamban; C517596:CAMK1 protein, human; C517658:CAMK2B protein, human; C517660:CAMK2D protein, human; C517662:CAMK2G protein, human; C517683:CAMK4 protein, human