Glucose-stimulated protein phosphorylation in the pancreatic islet.
A glucose-dependent phosphorylation of a 68kDa islet-cell protein was observed in islet-cell homogenates. In the presence of [gamma-32P]ATP the protein was phosphorylated only in the presence of alpha-D-glucose; other sugars were ineffective. Activation of the phosphorylation was half-maximal at 0.34 mM-glucose, 7 microM-ATP and 0.3 mM-Mg2+. Although the addition of glucose 6-phosphate in this design did not stimulate phosphorylation of the islet-cell protein, addition of glucose 6-phosphate to the radioactively labelled 68kDa protein rapidly removed (chased) the 32P label. The addition of presynthesized glucose 6-[32P]phosphate phosphorylated the 68kDa band in the islet-cell homogenate and also phosphorylated purified skeletal-muscle phosphoglucomutase. Phosphoglucomutase labelled thus by 32P was indistinguishable from the islet-cell phosphoprotein on electrophoretic gels. The 32P incorporated into both the islet-cell protein and the purified skeletal-muscle phosphoglucomutase was chased similarly by hexose phosphates. The purified phosphoglucomutase could also be phosphorylated by cyclic AMP-dependent protein kinase or by a mannoheptulose-insensitive process by the islet-cell cytosol. The phosphoenzyme formed thus was also dephosphorylated by D-glucose 6-phosphate and alpha-D-glucose 1-phosphate, suggesting that this may be a mechanism for generation of glucose 1,6-bisphosphate.
D000818:Animals; D005459:Fluorides / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology*; D006600:Hexosephosphates / Q000494:pharmacology; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008356:Mannoheptulose / Q000494:pharmacology; D010733:Phosphoglucomutase / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013268:Stimulation, Chemical
D006600:Hexosephosphates; D011506:Proteins; D008356:Mannoheptulose; D011494:Protein Kinases; D010733:Phosphoglucomutase; D005947:Glucose; D005459:Fluorides