Intracellular localization of phosphorylases in spinach and pea leaves.

Starch phosphorylase activity in extracts of spinach or pea leaves and of isolated chloroplasts was determined and separated by electrophoresis in polyacrylamide gels. In spinach leaf extracts, a specific activity of 16 nmol glucose 1-phosphate formed per min per mg protein was found, whereas a lower value (6 nmol per min per mg protein) was observed in preparations of isolated chloroplasts which were about 75% intact. In the spinach leaf extracts two forms of phosphorylase were found; chloroplast preparations almost exclusively contained one of these. In pea leaf extracts the specific activity was 10 nmol glucose 1-phosphate formed per min per mg protein. Three forms of phosphorylase contributed to this activity. Preparations of isolated chloroplasts with an intactness of about 85% exhibited a lower specific activity (5nmol per min per mg protein) and contained two of these three phosphorylase forms.