Figure 2.
In vitro enzyme activity and substrate specificity of four CEKs. A, Representative images of thin-layer chromatography plates indicating [32P]-labeled PCho or PEtn produced after incubating purified recombinant MBP-CEK1, MBP-CEK2, MBP-CEK3, and MBP-CEK4 with Cho or Etn in the presence of [γ-32P]ATP and Mg2+. The reaction with MBP but not CEK (lanes labeled MBP) or without adding protein (−) were used as negative controls. B, Specific activity of CEK isozymes in Cho or Etn kinase activity assay. Data are means ± sd from three replicates. Data obtained from at least three biologically independent experiments were analyzed by one-way ANOVA. Statistically different groups among conditions were further evaluated for significance with the Tukey’s honestly significant difference (HSD) mean separation test and displayed with lowercase letters indicating means that differ significantly. A level of P < 0.05 was considered significant. n.d., Not detected.