Activation by calmodulin of inositol-1,4,5-trisphosphate 3-kinase in guinea pig peritoneal macrophages

Yuichi Kimura, Masato Hirata, Koji Yamaguchi, Toshitaka Koga

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16 Citations (Scopus)


The activity of inositol-1,4,5-trisphosphate 3-kinase in the cytosol fraction of guinea pig macrophages was assayed with special reference to the dependence on the free Ca2+ concentration. The enzyme activity, as assessed by the production of inositol 1,3,4,5-tetrakisphosphate was reversibly activated by free Ca2+ concentrations ranging from 10-7 to 10-6m. The calmodulin antagonists, W-7 and chlorpromazine, inhibited the Ca2+-activated enzyme activity in a dose-dependent fashion, thereby indicating that calmodulin may be involved in the activation by Ca2+. The content of calmodulin in the cytosol fraction (about 2.8 μg/mg of cytosol protein) was markedly reduced to less than 0.03 μg/mg of proteins by subfractionation by ammonium sulfate, followed by an anionexchange chromatography. The subfraction obtained by the chromatography showed no Ca2+ dependence in the enzyme activity, while an exogenous addition of calmodulin with 10-6 m Ca-6 increased the enzyme activity. The enzyme activity was retained on a calmodulin-affinity column in the presence of Ca2+, and was eluted from the column by lowering the free Ca2+ concentration by adding ethylene glycol bis(β-aminoethyl ether)-N,N′-tetraacetic acid. These results clearly indicate that calmodulin activates the inositol-1,4,5-trisphosphate 3-kinase activity.

Original languageEnglish
Pages (from-to)363-369
Number of pages7
JournalArchives of Biochemistry and Biophysics
Issue number2
Publication statusPublished - Sept 1987

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Molecular Biology


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