Activation of the ATP.Mg-dependent type 1 protein phosphatase by the Fe2+/ascorbate system.
The ATP.Mg-dependent type 1 protein phosphatase is inactive as isolated but can be activated in several different ways. In this report, we show that the phosphatase can also be activated by the Fe2+/ascorbate system. Activation of the phosphatase requires both Fe2+ ion and ascorbate and the level of activation is dependent on the concentrations of Fe2+ ion and ascorbate. In the presence of 20 mM ascorbate, the Fe2+ ion concentrations required for half-maximal and maximal activation are about 0.3 and 3 mM, respectively. Several common divalent metal ions, including CO2+, Ni2+, Cu2+, Mg2+, and Ca2+ ions, cannot cooperate with ascorbate to activate the phosphatase, and SH-containing reducing agents such as 2-mercaptoethanol and dithiothreitol cannot cooperate with Fe2+ ion to activate the phosphatase, indicating that activation of the phosphatase by the Fe2+/ascorbate system is a specific process. Moreover, H2O2, a strong oxidizer, could significantly diminish the phosphatase activation by the Fe2+/ascorbate system, suggesting that reduction mechanism other than SH-SS interchange is a prerequisite for the Fe2+/ascorbate-mediated phosphatase activation. Taken together, the present study provides initial evidence for a new mode of type 1 protein phosphatase activation mechanism.
Department of Cell and Molecular Biology, Chang Gung College of Medicine and Technology, Tao-Yuan, Taiwan, ROC.
J S
JS
Yu
W H
WH
Chan
S D
SD
Yang
D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism / Q000494:pharmacology*; D002413:Cations, Divalent / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D004789:Enzyme Activation; D005296:Ferrous Compounds / Q000378:metabolism / Q000494:pharmacology*; D008623:Mercaptoethanol / Q000494:pharmacology; D010084:Oxidation-Reduction; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D013552:Swine
D002413:Cations, Divalent; D005296:Ferrous Compounds; D013438:Sulfhydryl Compounds; D008623:Mercaptoethanol; D010749:Phosphoprotein Phosphatases; D001205:Ascorbic Acid; D004229:Dithiothreitol