The Biosynthesis of Starch in Sugar Cane

Althougll starch poses a problem in the factory by retarding filtration and crystallization rates of cane juices (Balch, 1953; Feulherade, ~gzg) , little attention has been given the mechanisms of starch formation in sugarcane. Of further importance is the knowledge that both glucose-I-phosphate* and uridine diphospl~oglucose, themselves major precursors of sucrose, are also involved in starch biosynthesis. The process of starch formation might .thus compete with mechanisms of sucrose synthesis. In 1937 Cori and coworkers demonstrated that G-I-P was produced during the breakdown of glycogen by muscle extracts, and in so doing greatly advanced the understanding of polysaccharide transformations. Prior to that time, scientists believed that glycogen breakdown was mediated by amylases, hydrolytic enzymes which offered no reasonable explanation for polysaccharide formation. In 1940, Hanes discovered a phosphorylase which promotes the synthesis and degradation of starch in the pea seed and potato tuber. Catalyzing the reaction H,PO, + Starch G-I-P