| Popis: |
Phosphorylase II from potato tuber has been subjected to several purification procedures in order to: (a) separate the unprimed activity from the primed one coexisting in the enzymatic preparation, and (b) eliminate endogenous glucan and/or glycoproteins. Large-scale analytical nondenaturing gel electrophoresis and affinity chromatography on concanavalin A-Sepharose 4B succeeded in removing endogenous glycoproteins without any effect on the unprimed activity. In addition, phosphorolysis or glucoamylase treatment of the enzymatic preparation did not abolish the phosphorylase-catalyzed reaction in the absence of an exogenous acceptor. However, no separation between both activities, primed and unprimed, could be achieved either by the above-mentioned methods or by sucrose density gradient centrifugation. Based on sodium dodecyl sulfate-urea-gel electrophoresis, a molecular weight of about 96,000 was found for the phosphorylase II subunit. Molecular weight determination by nondenaturing gel electrophoresis at 5, 6, 7, and 8% acrylamide and by ultracentrifugation on sucrose density gradients suggested that the native enzyme is a dimer, as are other phosphorylases. |
