Roles of sucrose -metabolizing enzymes in accumulation of sugars in Cayenne pineapple fruit

The contents of sucrose, glucose and fructose, the activities of sucrose-metabolizing enzymes, including acid in-vertase(AI), neutral invertase (NI) , sucrose synthase(SS) and sucrose phosphate synthase(SPS) during fruit development process and the correlation between the sugar accumulation and the enzymes activity were studied in the fruit of pineapple cv. Cayenne. The results showed that the Cayenne fruit growth was in a sigmoid curve. Fructose and glucose accumulated sharply at the early stages, and sucrose accumulated slightly during the first and second stage of fruit development, which were re-alated to high invertase activities. However, at the ripening stage, sucrose accumulated sharply, while fructose and glucose slightly increased. Accumulation and compositions of sugars were affected evidently by the activities of SS and SPS in Cayenne fruit. The activities of acid invertase and neutral invertase were higher at the early developmental stage than at the late developmental stage; and the activities of sucrose synthase and sucrose phosphate synthase showed a similar change pattern with lower activities at the early developmental stage and higher activities at the late developmental stage. The correlation analyses showed that there was an extremely significant positive correlation between the content of sucrose and the activities of SS and SPS. A significant negative correlation was found between sucrose content and the activities of neutral and acid invertase.