Spinach Leaf Intra and Extra Chloroplast Phosphorylase Activities during Growth

The amino terminal sequence of the spinach (Spinacia oleracea L. cv Bloomsdale Long Standing) leaf cytoplasmic phosphorylase was determined and shown to have little similarity to the known sequence of the potato tuber phosphorylase. The antigenic reaction of spinach chloroplast phosphorylase and rabbit muscle phosphorylase a to antiserum prepared against spinach leaf cytoplasmic phosphorylase was tested. Neither phosphorylase gave a positive reaction when tested by immunodiffusion or neutralization of enzyme activity. The two spinach phosphorylases were assayed throughout the growth of the plant. Activity of cytoplasmic phosphorylase increased 4- to 8-fold at 30 to 35 days from sowing. Enzyme protein levels, as measured by antibody neutralization, increased by a similar amount. There was no corresponding increase in chloroplast phosphorylase activity. The chloroplast phosphorylase varied in parallel with the chloroplast enzyme ADPglucose pyrophosphorylase. Starch levels were high during the earlier stages of growth and then fell to a constant low level just before the increase in cytoplasmic phosphorylase. The results are discussed with respect to the relationship and functions of the two phosphorylases.