On the phosphorus of potato starch.

Native starches contain variable amounts of phosphorus. Samec and coworkers (1, 2) first showed that the phosphorus-containing components are not identical in all starches. In cereal starches most, if not all, of the phosphorus is contained in phosphatides which are loosely bound to the polysaccharide. Other starches such as potato, arrowroot, tapioca, and sago contain phosphorus esterified with some of the glucose units of the polysaccharide (3). Most of the phosphorus of potato starch seems to be contained in the branched (amylopectin) fraction (4, 5). Posternak (3) isolated glucose-g-phosphate after acid hydrolysis of tuber starches. Enzymatic degradation of potato starch with pancreatic amylase or with a mixture of CZand @amylase from malt yielded a phosphotetraose. When only a small amount of amylase was used, a phosphohexaose and phosphopolyoses with longer chains were obtained. When these isolated products were submitted to further action of cu-amylase they were converted to the phosphotetraose which represents therefore a degradation limit. The object of the present investigation was to determine the position of the glucoseB-phosphate units within the starch molecule. For this purpose the phosphopolyoses were isolated and subjected to structural analysis. Their priming effect on potato phosphorylase and t,he properties of the polysaccharide formed were also investigated.