Evolution of Sucrose Synthesis

Lunn, John E.

doi:10.1104/pp.010898

Cited by 96 publications

(107 citation statements)

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“…The Synechocystis SPP, like the plant enzyme, is competitively inhibited by sucrose (Lunn, 2002). The crystal structures clearly show that sucrose binds in the active site of the enzyme in a similar position to the substrate Suc6P, providing a simple explanation for the competitive nature of the inhibition.…”

Section: Specificity Of the Substrate Binding Site And Inhibition By mentioning

confidence: 84%

“…In the active site of the open conformation of the SPP structure, we observed a high electron density that we interpret to be a Mg 2þ ion, given the enzyme's dependence on Mg 2þ for catalytic activity and its high affinity for this metal ion (the activation constant is 70 mM; Lunn, 2002). Three Asp residues (Asp9 and Asp11 from motif I and Asp186 from motif III) and three water molecules participate in the coordination shell of this Mg 2þ ion ( Figure 4A).…”

Section: The Metal Ionmentioning

confidence: 97%

“…One of the most important properties of SPP is its ability to discriminate against Fru6P as a potential substrate (Lunn et al, 2000; Lunn, 2002), thus avoiding a futile cycle of Fru6P hydrolysis and resynthesis. The hydrolytic activity of the Synechocystis SPP with Fru6P as substrate is below the limit of detection with the standard assay (i.e., <0.5% of the activity with Suc6P), and no binding of Fru6P was observed when closed conformation crystals of the SPP were soaked with this potential ligand.…”

Section: Specificity Of the Substrate Binding Site And Inhibition By mentioning

confidence: 99%

“…The Synechocystis sp PCC 6803 SPP was expressed in Escherichia coli and partially purified as described by Lunn (2002). The partially purified protein was applied to a HiLoad 16/60 Superdex 200 column and equilibrated with buffer A (25 mM Hepes-K þ , 150 mM KCl, 5 mM MgCl 2 , and 0.5 mM EDTA, pH 7.2).…”

Section: Protein Expression and Purificationmentioning

confidence: 99%

“…We chose the enzyme from the cyanobacterium Synechocystis sp PCC 6803 because this can be readily expressed in Escherichia coli and purified to homogeneity in milligram amounts (Lunn, 2002). In the Synechocystis SPP, the conserved residues of HAD motifs I, II, and III are represented by DLDNTW (residues 9 to 14), LAYAT (37 to 41), and KX (21) GDSGND (163 to 190), respectively.…”

Section: Introductionmentioning

confidence: 99%

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The Structure of a Cyanobacterial Sucrose-Phosphatase Reveals the Sugar Tongs That Release Free Sucrose in the Cell

et al. 2005

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Sucrose-phosphatase (SPP) catalyzes the final step in the pathway of sucrose biosynthesis in both plants and cyanobacteria, and the SPPs from these two groups of organisms are closely related. We have crystallized the enzyme from the cyanobacterium Synechocystis sp PCC 6803 and determined its crystal structure alone and in complex with various ligands. The protein consists of a core domain containing the catalytic site and a smaller cap domain that contains a glucose binding site. Two flexible hinge loops link the two domains, forming a structure that resembles a pair of sugar tongs. The glucose binding site plays a major role in determining the enzyme's remarkable substrate specificity and is also important for its inhibition by sucrose and glucose. It is proposed that the catalytic reaction is initiated by nucleophilic attack on the substrate by Asp9 and involves formation of a covalent phospho-Asp9-enzyme intermediate. From modeling based on the SPP structure, we predict that the noncatalytic SPP-like domain of the Synechocystis sucrose-phosphate synthase could bind sucrose-6 F -phosphate and propose that this domain might be involved in metabolite channeling between the last two enzymes in the pathway of sucrose synthesis.

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Section: Specificity Of the Substrate Binding Site And Inhibition By mentioning

confidence: 84%

Section: The Metal Ionmentioning

confidence: 97%

Section: Specificity Of the Substrate Binding Site And Inhibition By mentioning

confidence: 99%

Section: Protein Expression and Purificationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The Structure of a Cyanobacterial Sucrose-Phosphatase Reveals the Sugar Tongs That Release Free Sucrose in the Cell

et al. 2005

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Structural and enzymatic analyses of Anabaena heterocyst‐specific alkaline invertase InvB

Xie

Cai

et al. 2018

FEBS Letters

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Anabaena sp. PCC 7120 encodes two alkaline/neutral invertases, namely InvA and InvB. Following our recently reported InvA structure, here we report the crystal structure of the heterocyst-specific InvB. Despite sharing an overall structure similar to InvA, InvB possesses a much higher catalytic activity. Structural comparisons of the catalytic pockets reveal that Arg430 of InvB adopts a different conformation, which may facilitate the deprotonation of the catalytic residue Glu415. We propose that the higher activity may be responsible for the vital role of InvB in heterocyst development and nitrogen fixation. Furthermore, phylogenetic analysis combined with activity assays also suggests the role of this highly conserved arginine in plants and cyanobacteria, as well as some proteobacteria living in highly extreme environments.

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Sucrose Metabolism

Lunn¹

2008

Encyclopedia of Life Sciences

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Sucrose is one of the main products of photosynthesis in plants, and the most common form of carbohydrate transported from source to sink organs. It also functions as a storage reserve, compatible solute and signal metabolite in plants. Sucrose is synthesized via the phosphorylated intermediate sucrose‐6′‐phosphate, by sucrose‐phosphate synthase (SPS) and sucrose‐phosphatase (SPP). In sink organs, sucrose is broken down by invertase or sucrose synthase to provide carbon and energy for growth and accumulation of storage reserves, such as starch, oil and fructans. Sucrose and trehalose are the only common nonreducing disaccharides found in nature, and their metabolism is inextricably linked in plants. Trehalose‐6‐phosphate, the intermediate of trehalose synthesis, is thought to act as a signal of sucrose availability in plant cells, and regulates the partitioning of photoassimilate between sucrose and starch in leaves and the utilization of sucrose in sink organs. Key concepts Sucrose is one of the main products of photosynthesis and the most common transport sugar in plants. Sucrose is a nonreducing disaccharide, and is synthesized in the cytosol via the phosphorylated intermediate, sucrose‐6′‐phosphate. In leaves, the rate of sucrose synthesis is tightly co‐ordinated with the rates of photosynthetic carbon dioxide fixation and starch synthesis in the chloroplasts. Sucrose is transported from leaves via the phloem, to provide the rest of the plant with carbon and energy for growth and storage product synthesis. Sucrose is unloaded from the phloem in sink organs. It can be hydrolyzed by cell wall invertases and imported into the cells as hexose sugars, or taken up intact and metabolized by intracellular invertases or sucrose synthase. Fructans are soluble polymers of fructose found in about 15% of all flowering plants. Dicotyledonous plants generally make inulin‐type fructans, whereas monocotyledonous plants also make levan, inulin neoseries, levan neoseries and mixed levan (graminan)‐type fructans. Fructans are synthesized from sucrose via trisaccharide intermediates – 1‐kestose, 6‐kestose or 6G‐kestose – by various fructosyltransferases in the vacuole. Trehalose is a nonreducing disaccharide found in many bacteria, archaea, invertebrates and fungi, and is often used as a stress protectant, compatible solute, storage reserve or transport sugar. Trehalose metabolism is ubiquitous in plants, and essential for their normal growth and development, but most flowering plants accumulate only trace amounts of trehalose. Trehalose‐6‐phosphate, the intermediate of trehalose synthesis, is a signal metabolite that reflects sucrose status in plants, and is involved in regulation of photoassimilate partitioning in leaves and the utilization of sucrose in sink organs.

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Evolution of Sucrose Synthesis

Cited by 96 publications

References 39 publications

The Structure of a Cyanobacterial Sucrose-Phosphatase Reveals the Sugar Tongs That Release Free Sucrose in the Cell

The Structure of a Cyanobacterial Sucrose-Phosphatase Reveals the Sugar Tongs That Release Free Sucrose in the Cell

Structural and enzymatic analyses of Anabaena heterocyst‐specific alkaline invertase InvB

Sucrose Metabolism

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