The Biosynthesis of Sucrose in Sugarcane

Abstract

Sucrose is formed from glucose-1-phosphate and fructose in the presence of tissue homogenates or undialyzed crude extracts from leaves of sugarcane. Optimum pH for the reaction is 8, although sucrose is formed readily from pH 7 to 9. Optimum concentrations of both glucose-1-phosphate and fructose lie in the area of 6 µmoles per milliliter of digest. Small quantities of sucrose are formed when either of the hexoses is added in the absence of the other. The reaction is stimulated by UTP, indicating that the formation of UDPG, and consequently the enzyme UDPG-fructose transglycosylase, is involved in sucrose production. UMP likewise stimulates the production of sucrose when added with ATP. DPN in cystein solution promotes the reaction in the presence of UDPG and ATP. There is no conclusive evidence that Mg, ATP, and DPN are required for sucrose production when added individually. ATP appears to promote glycolysis and retard sucrose formation under certain conditions, and promote sucrose production at other times by phosphorylative reactions.