Glycogen phosphorylase of potatoes purification and thermodynamic properties of the adsorption on glycogen

Abstract

1. 1.|Glycogen phosphorylase from potato tubers was purified by a rapid procedure including chromatography on starch grains followed by DEAE-Sephadex chromatography. 2. 2.|By gel filtration on Sephadex G-200 the purified enzyme showed a molecular weight of 180 000. Electrophoresis in gels with laurylsulphate revealed a molecular weight of 90 000 for the protein. 3. 3.|The enzyme activity with glycogen as a primer substrate is 30% higher than with starch. 4. 4.|Adsorption of the enzyme on glycogen and starch occurs over a pH region of pH 4–10. 5. 5.|Thermodynamic data were obtained for the adsorption of the glycogen phosphorylases 1 and 3 on glycogen by polyacrylamide-gel electrophoresis at different temperatures and with varying amounts of glycogen in the gels. The enthalpy change of the absorption is −58.6 kJ/mole for phosphorylase 3 and −66.5 kJ/mole for phosphorylase 1. The difference between the free energy change of the adsorption of isoenzymes 1 and 3 is 8.4 kJ/mole, whereas the entropy change is almost the same for both enzymes.