scholarly journals Apparent equilibrium constant and mass-action ratio for sucrose-phosphate synthase in seeds of Pisum sativum

1990 ◽  
Vol 267 (3) ◽  
pp. 739-743 ◽  
Author(s):  
J E Lunn ◽  
T ap Rees
Keyword(s):  
Pisum Sativum ◽  
Equilibrium Constant ◽  
Equilibrium Constants ◽  
Sucrose Phosphate Synthase ◽  
Mass Action ◽  
Apparent Equilibrium Constant ◽  
Apparent Equilibrium ◽  
Sucrose Phosphate ◽  
Phosphate Synthase

The aim of this work was to use preparations from germinating seeds of Pisum sativum to determine the apparent equilibrium constant of the reaction catalysed by sucrose-phosphate synthase (EC 2.4.1.14) and to compare this with the mass-action ratio of the reaction in the seeds. The apparent equilibrium constant ranged from 5.3 at 0.25 mM-MgCl2, pH 7.0, to 62 at 10 mM-MgCl2, pH 7.5. The sucrose phosphate content of the seeds, 23 nmol/g fresh wt., was determined by separating sucrose phosphate from sucrose by ion-exchange chromatography and then measuring the sucrose released by alkaline phosphatase. Comparison of equilibrium constants and mass-action ratios in the cotyledons of 38 h-germinated seeds showed that the reactions catalysed by glucose-6-phosphate isomerase, phosphoglucomutase and UDP-glucose pyrophosphorylase are close to equilibrium, and those catalysed by sucrose-phosphate synthase and sucrose phosphatase are considerably displaced from equilibrium in vivo.

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

1989 ◽  
Vol 323 (1216) ◽  
pp. 327-338 ◽  
Keyword(s):  
Sucrose Phosphate Synthase ◽  
Control Analysis ◽  
Sucrose Synthesis ◽  
Flux Control ◽  
Fructose 1,6 Bisphosphatase ◽  
Flux Control Coefficients ◽  
Sucrose Phosphate ◽  
Control Coefficients ◽  
Phosphate Synthase

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.

scholarly journals Site-specific serine phosphorylation of spinach leaf sucrose-phosphate synthase

1992 ◽  
Vol 283 (3) ◽  
pp. 877-882 ◽  
Author(s):  
J L A Huber ◽  
S C Huber
Keyword(s):  
Okadaic Acid ◽  
Spinacia Oleracea ◽  
Sucrose Phosphate Synthase ◽  
Serine Phosphorylation ◽  
Spinacia Oleracea L ◽  
Spinach Leaf ◽  
Sucrose Phosphate ◽  
Phosphate Synthase

We recently reported [Huber, Huber & Nielsen (1989) Arch. Biochem. Biophys. 270, 681-690] that spinach (Spinacia oleracea L.) sucrose-phosphate synthase (SPS; EC 2.4.1.14) was phosphorylated in vivo when leaves were fed [32P]Pi. In vitro the enzyme was phosphorylated and inactivated by using [gamma-32P]ATP. We now report that SPS is phosphorylated both in vivo and in vitro on serine residues. The protein is phosphorylated at multiple sites both in vivo and in vitro as indicated by two-dimensional peptide maps of the immunopurified SPS protein. After being fed with radiolabel, leaves were illuminated or given mannose (which activates the enzyme), in the presence or absence of okadaic acid. Feeding okadaic acid to leaves decreased the SPS activation state in the dark and light and in leaves fed mannose. Across all the treatments, the activation state of SPS in situ was inversely related to the labelling of two phosphopeptides (designated phosphopeptides 5 and 7). These two phosphopeptides are phosphorylated when SPS is inactivated in vitro with [gamma-32P]ATP, and thus are designated as regulatory (inhibitory) sites [Huber & Huber (1991) Biochim. Biophys. Acta 1091, 393-400]. Okadaic acid increased the total 32P-labelling of SPS and in particular increased labelling of the two regulatory sites, which explains the decline in activation state. In the presence of okadaic acid, two cryptic phosphorylation sites became labelled in vivo that were not apparent in the absence of the inhibitor. Overall, the results suggest that light/dark regulation of SPS activity occurs as a result of regulatory serine phosphorylation. Multiple sites are phosphorylated in vivo, but two sites in particular appear to regulate activity and dephosphorylation of these sites in vivo is sensitive to okadaic acid.

scholarly journals Identification of Factors Regulating the Phosphorylation Status of Sucrose-Phosphate Synthase in Vivo

1992 ◽  
Vol 99 (4) ◽  
pp. 1435-1442 ◽  
Author(s):  
Hendrik Weiner ◽  
Robert W. McMichael ◽  
Steven C. Huber
Keyword(s):  
Sucrose Phosphate Synthase ◽  
Sucrose Phosphate ◽  
Phosphate Synthase

Effects of canopy defoliation in the dark on the activity of sucrose phosphate synthase

1984 ◽  
Vol 34 (3) ◽  
pp. 247-252 ◽  
Author(s):  
Thomas W. Rufty ◽  
Steven C. Huber ◽  
Phillip S. Kerr
Keyword(s):  
Sucrose Phosphate Synthase ◽  
Sucrose Phosphate ◽  
Phosphate Synthase

scholarly journals Cloning and characterization of the Cerasus humilis sucrose phosphate synthase gene (ChSPS1)

PLoS ONE ◽  
2017 ◽  
Vol 12 (10) ◽  
pp. e0186650 ◽  
Author(s):  
Juan Wang ◽  
Junjie Du ◽  
Xiaopeng Mu ◽  
Pengfei Wang
Keyword(s):  
Sucrose Phosphate Synthase ◽  
Cerasus Humilis ◽  
Sucrose Phosphate ◽  
Phosphate Synthase
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