Adipose tissue protein phosphatase inhibitor-2.
Rat fat cells contain three species of spontaneously active inhibitor proteins of protein phosphatase 1, as resolved by SDS-PAGE, with apparent molecular masses of 40 kDa, and 28 kDa respectively. The 33-kDa, thermostable inhibitor was highly purified from bovine adipose tissue and shown to be very similar to inhibitor-2 of skeletal muscle. It was phosphorylated, on threonine only, by glycogen synthase kinase 3. It formed an inactivated complex with protein phosphatase 1, that was reactivated by incubation with ATP-Mg and glycogen synthase kinase 3. By gel filtration it had a Stokes radius of 3.4 nm. Peptide and phosphopeptide maps, generated by Staphylococcus aureus V8 proteinase, trypsin or thermolysin, of the inhibitor and of the skeletal muscle inhibitor-2 were similar. The 40-kDa inhibitor, which was denatured by boiling, represents a novel protein phosphatase inhibitor protein or an undegraded precursor of inhibitor-2. The total activity of inhibitor-2-like material (thermostable and macromolecular) in an adipocyte cytosol extract corresponded to an intracellular concentration of 0.3 microM inhibitor-2.
Strålfors
P
P
Department of Physiological Chemistry, University of Lund, Sweden.
D000273:Adipose Tissue / Q000201:enzymology*; D000818:Animals; D002417:Cattle; D004791:Enzyme Inhibitors / Q000302:isolation & purification*; D008970:Molecular Weight; D010449:Peptide Mapping; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010750:Phosphoproteins / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis; D054645:Protein Phosphatase 1; D011506:Proteins / Q000302:isolation & purification*; D000097847:Protein Phosphatase Inhibitory Proteins
D004791:Enzyme Inhibitors; D010749:Phosphoprotein Phosphatases; D010750:Phosphoproteins; D010769:Phosphothreonine; D054645:Protein Phosphatase 1; D011506:Proteins; C024833:protein phosphatase inhibitor-2; D000097847:Protein Phosphatase Inhibitory Proteins