Relationship Between Sucrose Accumulation and Sucrose-Metabolizing Enzymes in Developing Grapes

Abstract

The present study examined sugar accumulation and changes in sucrose-metabolizing enzyme activity (acid invertase, sucrose synthase and sucrose phosphate synthase) in the skin and flesh tissues of Steuben and Muscat Bailey A (Bailey x Muscat Hamburg) grapes during development. Sucrose accounted for 18.6% and 31.3% of total sugars in the flesh and skin tissues, respectively, in Steuben grapes and 2.0% and 16.2%, respectively, in Muscat Bailey A grapes. Sucrose synthase and sucrose phosphate synthase activity in- creased with development in both types of grapes, but this increase was small. The significant enzymic difference between Muscat Bailey A and Steuben grapes exists at the level of acid invertase activity; acid invertase activity in Muscat Bailey A increased and reached a maximum at the beginning of sugar accumula- tion and then decreased, whereas that in Steuben grapes decreased with development and remained much lower than that of Muscat Bailey A. These results suggest that the higher proportion of sucrose in Steuben grapes is associated with a lower acid invertase activity.