Studies on Enzymatically Modified Branched Polysaccharides. I. Star‐shaped Polymers with Glycogen and Amylopectin Containing Branches Elongated by Phorsphorylase.Star‐shaped glycogen and amylopectin molecules containing branches elongated with potato phosphorylase are characterized by light scattering and viscosity measurements, iodine binding properties and retrogradation rate in aqueous solution. Suitable methods for the evaluation of number and lengths of newly synthesized branches are discussed. It was found that potato phosphorylase utilizes only 15–20 of the glycogen end groups whereas all of the amylopectin end groups are available for synthesis. An increase in retrogradation rate and dichroic absorption of the iodine complex with decreasing branch lengths was observed as for free am