Control Analysis of Photosynthetic Sucrose Synthesis: Assignment of Elasticity Coefficients and Flux-Control Coefficients to the Cytosolic Fructose 1,6-Bisphosphatase and Sucrose Phosphate Synthase

• Published in: Philosophical transactions of the Royal Society of London. Series B, Biological sciences Biological sciences, 1989-04, Vol.323 (1216), p.327-338
• Main Author: Stitt, M.
• Format: Article
• Language: English
• Subjects: Connectivity; Cytosol; Enzyme substrates; Enzymes; Gene expression regulation; Hexoses; Phosphates; Photosynthesis; Physiological regulation; Spinach
• ISSN: 0962-8436; 0080-4622; 1471-2970; 2054-0280
• DOI: 10.1098/rstb.1989.0014

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 $\alpha$, describing the response of the fructose 2,6-bisphosphate regulator cycle to fructose 6-phosphate is described, and an expression is derived relating $\alpha$ to the elasticities of the enzymes involved in this regulator cycle.. The in vivo values for elasticities and $\alpha$ 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.