ACTIVITIES OF SUCROSE METABOLIZING ENZYMES DURING SUCROSE ACCUMULATION IN DEVELOPING ACID LIMES

The development of acid lime juice cells was characterised by a transient accumulation of sucrose. The capacity for sucrose synthesis and/or sucrose breakdown was estimated by measuring the maximal activities of sucrose synthesising (sucrose phosphate synthase, SPS) and sucrose degradative (sucrose synthase (SS), acid and alkaline invertase) enzymes throughout development. The maximal potential for sucrose breakdown always exceeded the potential for sucrose synthesis. When SS was assayed in the breakdown direction and acid invertase at physiological vacuolar pH values, the balance of the sucrose metabolising enzymes paralleled the patterns of sucrose accumulation in the fruit throughout development. Results show that in acid lime juice cells the potential for sucrose accumulation is linked to the activities of sucrose metabolising enzymes as modified by intracellular conditions and not to their maximal activities.