Starch in Storage Tissues

Amylopectin molecules are large flattened disks consisting of (1 —4)-linked a-glucan chains joined by frequent 6)-branch points. Many models of amylopectin structure have been proposed. The most satisfactory models are those proposed by Robin et al.,18 Manners and Matheson,19 and Hizukuri 20 all are known as cluster models. Reviews by Morrison and Karkalis21 and Hizukuri22 discuss in detail the chemical and physical aspects of the starch granule and its components, amylose and amylopectin. 

Synthesis in Plants and Algae and Glycogen Synthesis in Cyanobacteria 

Elongated (1 — 4)-linked malto-oligosaccharide chain — (1— 4,1— -6) branched a-glucan (4.3) 

Reaction 4.2 is catalyzed by starch synthase (E.C. 2.4.1.21 ADP-glucose 1,4-a-D-glucan 4-a-glucosyltransferase). Similar reactions are noted for glycogen synthesis in cyanobacteria and other bacteria,24 26 but the enzyme is referred to as glycogen synthase (also E.C. 2.4.1.21). 

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