Formation of a soluble amylopectin-like polysaccharide in potato tubers.

When potato sprouts or potato tuber slices were incubated with 0.1 m glucose 1-phosphate, a soluble amylopectin-like polysaccharide was excreted to the medium. This polysaccharide was found to be a very good primer for phosphorylase and a poor one for starch synthetase. Beside the formation of this extracellular polysaccharide, a more branched intracellular polysaccharide could be isolated. This polysaccharide was an excellent primer for starch synthetase. Fructose 6-phosphate, glucose 6-phosphate, fructose 1,6-diphosphate, glucose or sucrose could not substitute for glucose 1-phosphate. 2,4-Dinitrophenol or nitrogen did not affect the excretion of the polysaccharide. Some properties of these 2 polysaccharides are described.