칼슘/칼모듈린-의존성 단백질 키나아제 I 키나아제에 의한 칼슘/칼모듈린-의존성 단백질 키나아제 Ia의 활성화에 따른 효소반응 특성의 변화

Changes in Kinetic Properties of Ca2+/Calmodulin-Dependent Protein Kinase Ia Activated by Ca2+/Calmodulin-Dependent Protein Kinase I Kinase

The activity of Ca2+/calmodulin (CaM)-dependent protein kinase Ia (CaM kinase Ia) is shown to be regulated through direct phosphorylation by CaM kinase I kinase (CaMKIK). In the present study, three distinct CaMKIK peaks were separated from Q-Sepharose colunm chromatography of pig brain homogenate using a Waters 650 Protein Purification System. The purified CaMKIK from the major peak potently and rapidly enhanced CaM kinase Ia activity, reaching a maximal stimulation within 2min at the concentrations of 12-15nM. The activated state of CaM kinase Ia is characterized by a markedly enhanced Vmax as well as significantly decreased Km and Ka values toward peptide substrate and CaM, respectively. These observations suggest the activation process of CaM kinase Ia. The phosphorylation of CaM kinase Ia by CaMKIK may induce its conformational change responsible for the alterations in the kinetic properties, which ultimately leads to the rapid enzyme activation.