title: Selective modulation of the two antagonistic activities of protein kinase FA (the activator of ATP.Mg-dependent protein phosphatase).
abstract: The ATP.Mg-dependent protein phosphatase activating factor (FA) has been identified as a protein kinase. The results are unexpected since factor FA possesses two activities which are antagonistic. As a kinase, factor FA catalyzes protein phosphorylation, while as a phosphatase activator, it catalyzes protein dephosphorylation. In this report, we found that the two opposing activities of factor FA could be selectively modulated. For instance, heparin at concentrations of 0.1-0.3 mg/ml could stimulate FA to work preferentially as a kinase towards phosphorylation of proteins but simultaneously inhibit it to work as a phosphatase activator towards dephosphorylation of the same proteins. In a similar manner, alkaline pH could stimulate FA to work as a kinase but block it to work as a phosphatase activator. This is the first report providing initial evidence that the two opposing activities of factor FA can be selectively modulated in a reciprocal manner by various triggers, suggesting that a simultaneous coordinate control mechanism may well be involved in regulating the activities of factor FA in the cell.
authors.affiliation: Institute of Life Sciences, National Tsing Hua University, Hsinchu, Taiwan, ROC.
authors.forename: S D
authors.initials: SD
authors.lastname: Yang
authors.forename: J S
authors.initials: JS
authors.lastname: Song
authors.forename: Y T
authors.initials: YT
authors.lastname: Hsieh
authors.forename: H W
authors.initials: HW
authors.lastname: Liu
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000378:metabolism; D002417:Cattle; D004533:Egtazic Acid / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3; D006493:Heparin / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*
chemical_list: D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D006493:Heparin; D011494:Protein Kinases; D038362:Glycogen Synthase Kinase 3