General Metabolism of Starch

Two catabolic pathways of starch are known. One is hydrolytic, and involves two amylases  

Starch degradation in dicot seeds yields more glucose and maltotriose than that in cereals, where more maltose is produced. This is related, in part, to the relative activity of jS-amylase in the two classes of seeds. 

Let us now consider some details of these breakdown processes. 

Starch phosphorylase incorporates phosphate, rather than water, across the a-1,4 linkage between the penultimate and last glucose at the non-reducing end of the polysaccharide chain. One molecule of glucose-1-phosphate is released. This enzyme attacks amylose repetitively and amylopectin can be degraded to within two or three glucose residues of a a-1,6 branch linkage. 

---