Effects of Phosphatase Inhibitors on Mammalian p34cdc2 Kinase Activities

  • Xiao-Wen Guo
  • John P. H. Th’ng
  • Richard A. Swank
  • E. Morton Bradbury
Part of the GWUMC Department of Biochemistry Annual Spring Symposia book series (GWUN)


The activity of cyclin-dependent protein kinase p34cdc2 is regulated by phosphorylation. in this study, we show that the presence of phosphatase inhibitors can have major effects on the levels of phosphorylation and the activities of the kinase extracted from cells. The combination of okadaic acid and sodium vanadate was most effective in protecting p34cdc2 against cellular phosphatases. in the absence of these inhibitors, p34cdc2 was dephosphorylated with an altered activity, indicating that phosphatase activities remained high during extractions. in contrast to when both inhibitors were used, lower activity of the kinase was found when only sodium vanadate was used, whereas higher activity was found in the presence of okadaic acid. Other conventional phosphatase inhibitors such as NaF, NaHSO3 and glycerol 2-phosphate, were not effective in preventing dephosphorylation from p34cdc2 in whole cell lysates.


Protein Phosphatase Phosphatase Inhibitor Okadaic Acid Zinc Chloride Sodium Vanadate 
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Copyright information

© Springer Science+Business Media New York 1994

Authors and Affiliations

  • Xiao-Wen Guo
    • 1
  • John P. H. Th’ng
    • 1
  • Richard A. Swank
    • 1
  • E. Morton Bradbury
    • 1
    • 2
  1. 1.Department of Biological Chemistry, School of MedicineUniversity of CaliforniaDavisUSA
  2. 2.Division of Life SciencesLos Alamos National LaboratoriesLos AlamosUSA

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