The use of elasticity coefficients and flux-control coefficients in a quantitative treatment of control is discussed, with photosynthetic sucrose synthesis as an example. Experimental values for elasticities for the cytosolic fructose 1,6-bisphosphatase and sucrose phosphate synthase are derived from their
in vitro
properties, and from an analysis of the
in vivo
relation between fluxes and metabolite levels. An empirical factor
α
, describing the response of the fructose 2,6-bisphosphate regulator cycle to fructose 6-phosphate is described, and an expression is derived relating
α
to the elasticities of the enzymes involved in this regulator cycle. The
in vivo
values for elasticities and
α
are then used in a modified form of the connectivity theorem to estimate the flux control coefficients of the cytosolic fructose 1,6-bisphosphatase and sucrose phosphate synthase during rapid photosynthetic sucrose synthesis.
Understanding the molecular mechanism of transcriptional regulation of banana Sucrose phosphate synthase (SPS) gene during fruit ripening: an insight into the functions of variouscis-acting regulatory elements