The major acidic fibroblast growth factor (aFGF)-stimulated phosphoprotein from bovine liver plasma membranes has aFGF-stimulated kinase, autoadenylylation, and alkaline nucleotide phosphodiesterase activities.
The major acidic fibroblast growth factor (aFGF)-stimulated phosphoprotein (MAFP) purified from bovine liver exhibits kinase, autoadenylylation, and alkaline nucleotide phosphodiesterase activities depending upon reaction conditions. In the presence of divalent ions, MAFP showed intrinsic and a FGF-stimulated kinase activities (autophosphorylation) using either [gamma-32P]ATP or [gamma-32P]GTP as a substrate. The autophosphorylation activity of MAFP was stimulated at low concentrations of Ca2+, Mg2+, or Mn2+ (0.2-2 microM). Depletion of the divalent ions by EDTA abolished the autophosphorylation activity but enhanced the autoadenylylation activity of MAFP. [alpha-32P]ATP as well as [alpha-32P]NAD could serve as substrates for autoadenylylation activity of MAFP. aFGF appeared to enhance the autoadenylylation activity of MAFP with an optimal concentration (0.6-1.2 nM). P1, P3-di(adenosine-5')-triphosphate (AP3A) was found to be a potent inhibitor for the autophosphorylation and autoadenylylation activities of MAFP. Analyses by automated Edman degradation of the adenylylated and phosphorylated peptides derived from autoadenylylated and autophosphorylated MAFP revealed that both autoadenylylation and autophosphorylation occurred at residue Thr204. The kinase and autoadenylylation activities of MAFP had an optimal pH of 6.9-7.4. However, at pH 8.9, MAFP showed intrinsic and aFGF-stimulated phosphodiesterase activities. aFGF appeared to stimulate the phosphodiesterase activity of MAFP without altering the Km (approximately 0.2 mM) of its substrate.
Oda
Y
Y
Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, Missouri 63104.
Kuo
M D
MD
Huang
S S
SS
Huang
J S
JS
D000225:Adenine / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002413:Cations, Divalent; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D004492:Edetic Acid; D004789:Enzyme Activation; D016220:Fibroblast Growth Factor 1 / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000201:enzymology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011755:Pyrophosphatases; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism
D002413:Cations, Divalent; D008562:Membrane Glycoproteins; D016220:Fibroblast Growth Factor 1; D013912:Threonine; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D004492:Edetic Acid; D011494:Protein Kinases; D010727:Phosphoric Diester Hydrolases; C065962:ectonucleotide pyrophosphatase phosphodiesterase 1; D011755:Pyrophosphatases; D000225:Adenine