Data from: Model-assisted analysis of sugar metabolism throughout tomato fruit development reveals enzyme and carrier properties in relation to vacuole expansion

A kinetic model combining enzyme activity measurements and subcellular
compartmentation was parameterized to fit the sucrose, hexose, and
glucose-6-P contents of pericarp throughout tomato (Solanum lycopersicum)
fruit development. The model was further validated using independent data
obtained from domesticated and wild tomato species and on transgenic
lines. A hierarchical clustering analysis of the calculated fluxes and
enzyme capacities together revealed stage-dependent features. Cell
division was characterized by a high sucrolytic activity of the vacuole,
whereas sucrose cleavage during expansion was sustained by both sucrose
synthase and neutral invertase, associated with minimal futile cycling.
Most importantly, a tight correlation between flux rate and enzyme
capacity was found for fructokinase and PPi-dependent phosphofructokinase
during cell division and for sucrose synthase, UDP-glucopyrophosphorylase,
and phosphoglucomutase during expansion, thus suggesting an adaptation of
enzyme abundance to metabolic needs. In contrast, for most enzymes, flux
rates varied irrespectively of enzyme capacities, and most enzymes
functioned at <5% of their maximal catalytic capacity. One of the
major findings with the model was the high accumulation of soluble sugars
within the vacuole together with organic acids, thus enabling the
osmotic-driven vacuole expansion that was found during cell division.