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Spinach (Spinacia oleracea) chloroplast sedoheptulose-1,7-bisphosphatase. Activation and deactivation, and immunological relationship to fructose-1,6-bisphosphatase.

ABSTRACT: In this paper we study activation by dithiothreitol and reduced thioredoxins and deactivation by oxidized thioredoxins f of sedoheptulose-1,7-bisphosphatase. The behaviour of the enzyme when chromatographed on a thioredoxin-Sepharose column is also described. The enzyme is autoxidizable upon removal of reducing agents, and is activated when reduced by any of the thioredoxins. This mechanism may allow the regulation of the Calvin cycle upon light-dark and dark-light transitions. The formation of a stable complex between enzyme and thioredoxin could explain the inhibitory effect of high thioredoxin concentrations. The use of immunological techniques shows that sedoheptulose-1,7-bisphosphatase and fructose-1,6-bisphosphatase are poorly related immunologically.

SUBMITTER: Cadet F

PROVIDER: S-EPMC1149281 | biostudies-other | 1988 Jul

REPOSITORIES: biostudies-other

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pH and kinetic studies of chloroplast sedoheptulose-1,7-bisphosphatase from spinach (Spinacia oleracea).

Project description:The aim of this paper is to study some steady-state kinetic properties of sedoheptulose-1,7-bisphosphatase, its pH-dependence and the effect of a substrate analogue, fructose 2,6-bisphosphate. Studies were carried out with sedoheptulose 1,7-bisphosphate and with fructose 1,6-bisphosphate, an alternative substrate. The pK values are identical for both substrates, and fructose 2,6-bisphosphate behaves like a competitive inhibitor. These results suggest that there exists a unique active site for either sedoheptulose 1,7-bisphosphate or fructose 1,6-bisphosphate on the enzyme molecule. Increasing Mg2+ concentrations shifted the optimum pH. As for fructose-1,6-bisphosphatase, we believe that this shift is due to the neutralization of negative charges near the active centre [Cadet, Meunier & Ferté (1987) Eur. J. Biochem. 162, 393-398]. The free species of sedoheptulose 1,7-bisphosphate and fructose 1,6-bisphosphate are not the usual substrates of enzyme, nor is Mg2+. But the kinetics relative to the (Mg2+-substrate4-)2- complex is not consistent with this complex being the substrate. An explanation of this discrepancy is proposed, involving both the negative charges near the active centre and the positive charges of Mg2+. The observed Vmax. of the reduced enzyme is 65% of the theoretical Vmax. for both substrates, but the observed Vmax. relative to sedoheptulose 1,7-bisphosphate is 3 times the one relative to fructose 1,6-bisphosphate. The specificity constant (kcat./Km), 1.62 x 10(6) M-1.s-1 with respect to sedoheptulose 1,7-bisphosphate compared with 5.5 x 10(4) M-1.s-1 with respect to fructose 1,6-bisphosphate, indicates that the enzyme specificity towards sedoheptulose 1,7-bisphosphate is high but not absolute.

| S-EPMC1149282 | biostudies-other

Isolation and purification of chloroplastic spinach (Spinacia oleracea) sedoheptulose-1,7-bisphosphatase.

Project description:Higher-plant sedoheptulose-1,7-bisphosphatase was isolated and purified over 200-fold from spinach (Spinacia oleracea) chloroplast stromal extracts to apparent electrophoretic homogeneity by DEAE-Fractogel, molecular sieving on Sephadex G-200 and Blue B dye-matrix affinity chromatography. It is a protein of Mr 66,000, made up of two apparently identical subunits (Mr 35,000). The enzyme is activated by reduced thioredoxin fb in the presence of dithiothreitol. Its specificity towards sedoheptulose 1,7-bisphosphate versus fructose 1,6-bisphosphate is high, but not absolute.

| S-EPMC1147525 | biostudies-other

Properties of oxidized and reduced spinach (Spinacia oleracea) chloroplast fructose-1,6-bisphosphatase activated by various agents.

Project description:Fructose-1,6-bisphosphatase (FBPase) can be reduced and activated by either dithiothreitol or reduced thioredoxin. This activation is pH-dependent. An amino acid group with a pK value of 5.55 is involved in this process. Both enzyme forms can also be stimulated by agents such as fructose 1,6-bisphosphate, Mg2+, Ca2+ and Ca2+/fructose 1,6-bisphosphate. FBPase reduced by dithiothreitol is more strongly activated than the enzyme reduced by thioredoxin. The specificity constant (kcat./Km) is enhanced over 2.5-25-fold and 1.5-2-fold (depending on the agent used) for FBPase reduced by dithiothreitol and thioredoxin respectively. In both cases, no new kinetic properties appeared. The pH-activity profile of the stimulated enzyme is slightly shifted towards the acidic side with respect to the reduced enzyme. A lag phase is observed in the progress curve of both enzymic forms, treated or untreated. Each agent used to stimulate must induce a new conformation of the enzyme, more active than the initial one, characterized by a specificity constant and a relaxation time. This lag phase tends to disappear when the assay temperature is increased. Temperature has the same effect on the activity of oxidized, reduced and stimulated FBPase, but different effects on the stability of the different forms.

| S-EPMC1151415 | biostudies-other

Effect of hydrogen peroxide on spinach (Spinacia oleracea) chloroplast fructose bisphosphatase.

Project description:Thiol-treated spinach (Spinacia oleracea) chloroplast fructose bisphosphatase (EC 3.1.3.11) is severely inhibited by H2O2, whereas the freshly purified enzyme is little affected. Dithiothreitol reverses inhibition by H2O2, indicating that essential thiol groups are oxidized during H2O2 inactivation. A new role for the dithiol and thioredoxin systems that are operative in illuminated chloroplasts is proposed.

| S-EPMC1162009 | biostudies-other

Structure of the dual-function fructose-1,6/sedoheptulose-1,7-bisphosphatase from Thermosynechococcus elongatus bound with sedoheptulose-7-phosphate.

Project description:The dual-function fructose-1,6/sedoheptulose-1,7-bisphosphatase (FBP/SBPase) in cyanobacteria carries out two activities in the Calvin cycle. Structures of this enzyme from the cyanobacterium Synechocystis sp. PCC 6803 exist, but only with adenosine monophosphate (AMP) or fructose-1,6-bisphosphate and AMP bound. The mechanisms which control both selectivity between the two sugars and the structural mechanisms for redox control are still unresolved. Here, the structure of the dual-function FBP/SBPase from the thermophilic cyanobacterium Thermosynechococcus elongatus is presented with sedoheptulose-7-phosphate bound and in the absence of AMP. The structure is globally very similar to the Synechocystis sp. PCC 6803 enzyme, but highlights features of selectivity at the active site and loop ordering at the AMP-binding site. Understanding the selectivity and control of this enzyme is critical for understanding the Calvin cycle in cyanobacteria and for possible biotechnological application in plants.

| S-EPMC4601601 | biostudies-literature

Characterization of fructose 1,6-bisphosphatase and sedoheptulose 1,7-bisphosphatase from the facultative ribulose monophosphate cycle methylotroph Bacillus methanolicus.

Project description:The genome of the facultative ribulose monophosphate (RuMP) cycle methylotroph Bacillus methanolicus encodes two bisphosphatases (GlpX), one on the chromosome (GlpX(C)) and one on plasmid pBM19 (GlpX(P)), which is required for methylotrophy. Both enzymes were purified from recombinant Escherichia coli and were shown to be active as fructose 1,6-bisphosphatases (FBPases). The FBPase-negative Corynebacterium glutamicum ?fbp mutant could be phenotypically complemented with glpX(C) and glpX(P) from B. methanolicus. GlpX(P) and GlpX(C) share similar functional properties, as they were found here to be active as homotetramers in vitro, activated by Mn(2+) ions and inhibited by Li(+), but differed in terms of the kinetic parameters. GlpX(C) showed a much higher catalytic efficiency and a lower Km for fructose 1,6-bisphosphate (86.3 s(-1) mM(-1) and 14 ± 0.5 ?M, respectively) than GlpX(P) (8.8 s(-1) mM(-1) and 440 ± 7.6 ?M, respectively), indicating that GlpX(C) is the major FBPase of B. methanolicus. Both enzymes were tested for activity as sedoheptulose 1,7-bisphosphatase (SBPase), since a SBPase variant of the ribulose monophosphate cycle has been proposed for B. methanolicus. The substrate for the SBPase reaction, sedoheptulose 1,7-bisphosphate, could be synthesized in vitro by using both fructose 1,6-bisphosphate aldolase proteins from B. methanolicus. Evidence for activity as an SBPase could be obtained for GlpX(P) but not for GlpX(C). Based on these in vitro data, GlpX(P) is a promiscuous SBPase/FBPase and might function in the RuMP cycle of B. methanolicus.

| S-EPMC3811596 | biostudies-literature

Action of calcium ions on spinach (Spinacia oleracea) chloroplast fructose bisphosphatase and other enzymes of the Calvin cycle.

Project description:Thiol-treated spinach (Spinacia oleracea) chloroplast fructose bisphosphatase is powerfully inhibited by Ca2+ non-competitively with respect to its substrate, fructose 1,6-bisphosphate. 500 microM-Ca2+ causes virtually complete inhibition and the Ki is 40 microM. Severe inhibition of sedoheptulose bisphosphatase is also caused by Ca2+. A role for Ca2+ in regulation of the Calvin cycle in spinach chloroplasts is proposed.

| S-EPMC1161961 | biostudies-other

The complete mitochondrial genome sequence of spinach, <i>Spinacia oleracea</i> L.

Project description:Spinach (Spinacia oleracea L.) is an economically important vegetable crop. Here we describe the complete mitochondrial DNA sequence of spinach, which has a length of 329,613 bp and a GC content of 43.4%. It is separated by a pair of directly repeated elements of 7286 bp, to form a large single copy region of 229,375 bp and a small single copy region of 85,666 bp. The genome contains 29 protein-coding genes, 4 pseudogenes, 24 tRNA genes, and 3 rRNA genes. A phylogenetic analysis revealed that spinach was closely related to Beta vulgaris (sugar beet), both belonging to the Amaranthaceae family.

| S-EPMC7799700 | biostudies-literature

Direct desaturation of intact galactolipids by a desaturase solubilized from spinach (Spinacia oleracea) chloroplast envelopes.

Project description:In plants, polyenoic fatty acids are synthesized by desaturase enzymes which use acyl groups of membrane lipids as substrates. To provide direct 'in vitro' evidence for this reaction, we solubilized envelope membranes from spinach (Spinacia oleracea) chloroplasts with Triton X-100 to release a membrane-bound n-6 desaturase. In the presence of oxygen and reduced ferredoxin, the solubilized enzyme desaturated a variety of substrates, such as free oleic acid, free erucic acid, 1-oleoyl-sn-glycerol 3-phosphate and the three galactolipids 1-oleoyl-2-(7'-cis-hexadecenoyl)-3-beta-D-galactopyranosyl-sn-glycerol, 1,2-dioleoyl-3-beta-D-galactopyranosyl-sn-glycerol and the ether analogue 1,2-di-(9'-cis-octadecenyl)-3-beta-D-galactopyranosyl-sn- glycerol. The in vitro desaturation of these exogenously added complex lipids with ester- and ether-linked substrate chains is unambiguous evidence for lipid-linked desaturation. The enzyme measures the insertion of the new double bond from the methyl end and the existing (n-9)-cis-double bond of an appropriate acyl or alkyl chain. The distal part of the substrate group, normally the carboxy end of a fatty acyl residue, is of less importance and, in particular, its activation in thioester form is not required.

| S-EPMC1132243 | biostudies-other

Heat-induced alternations in proteomic and transcriptomic profiles of spinach (Spinacia oleracea)

Project description:Spinach (Spinacia oleracea L.) is an economically important and globally consumed popular leafy vegetable that is heat-sensitive. Heat stress caused by global climate change is one of the primary deleterious elements limiting spinach production worldwide. Little work has been done to explore the heat-responsive mechanisms of spinach under high temperature-induced stress. In the present study, we used iTRAQ-based proteomic and transcriptomic approaches to investigate physiological, metabolic, and proteomic responses of spinach in response to day / night temperature of 35°C / 25°C compared to 20°C / 15°C for 4 days. A total of 3,543 differentially expressed genes (DEGs) were detected using transcriptome sequencing, of which 2,086 DEGs were downregulated and 1,457 were upregulated. The DEGs were mainly involved in superoxide dismutase activity, catalase, and peroxidase activity. A total of 3,246 differentially abundant proteins were detected using iTAQ-based quantitative proteomic approach, from which 567 differentially expressed proteins (DEPs) (277 upregulated and 290 downregulated) were identified. DEPs were mainly assigned to pathways related to metabolism, signal transduction, protein degradation, defense, and antioxidant. Four genes - superoxide dismutase (SOD, LOC110788339), catalase (CAT, LOC110790286), peroxidase (POD, LOC110775253), and heat shock protein (HSP, LOC110799288) - were validated using quantitative real-time PCR (qRT-PCR) to verify the proteomic and transcriptomic analyses, showing different transcriptional and translational expression levels. The findings of this study provide a fundamental understanding of the metabolic pathways and biological processes that control adaptation to heat stress in spinach, and provide novel insight into the development of heat-tolerant spinach.

2020-06-24 | GSE153070 | GEO

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