Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.1.14 (SPS)
 813 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the experiments reported in this paper, we characterised the physiological and biochemical factors involved in the chilling-induced inhibition of photosynthetic carbon metabolism in soybean [Glycine max (L.) Merr.] genotypes of temperate and tropical adaptation. Plants of Maple Arrow (temperate genotype) and Java 29 (tropical genotype) were exposed to a single night at 8 degrees C. Dark chilling resulted in the inhibition of diurnal CO2 assimilation rate and decreased stomatal conductance in both genotypes. Further analysis, however, revealed a difference in the response of the two genotypes. Stomatal limitation was largely responsible for the inhibition of CO2 assimilation in Maple Arrow, whereas mesophyll limitation dominated the inhibition in Java 29. The results indicate that inhibition of stromal fructose-1,6-bisphosphatase (sFBPase; EC 3.1.3.11) activity and impaired electron transport capacity were responsible for the decrease in ribulose-1,5-bisphosphate (RuBP) regeneration capacity in Java 29. Sucrose-phosphate synthase (SPS; EC 2.4.1.14) activity was progressively inhibited during the light period in this genotype and might impose an additional constraint on photosynthesis. Maple Arrow appears to possess, at least with respect to photosynthetic carbon metabolism, physiological and biochemical characteristics that contribute towards its superior dark chilling tolerance.
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PMID:Limitation of photosynthetic carbon metabolism by dark chilling in temperate and tropical soybean genotypes. 1528 27

Carbon assimilation, translocation, and associated biochemical characteristics of the second trifoliolate leaf (numbered acropetally) of chamber-grown soybean, Glycine max (L.) Merr., plants were studied at selected stages of leaf development during the period from 10 to 25 days postemergence. Leaves of uniform age were selected on the basis of leaf plastochron index (LPI).The test leaf reached full expansion (A(max)) and maximum CO(2) exchange rates on a leaf area basis at 17 days postemergence (LPI 4.1). Maximum carbon exchange rates per unit dry weight of lamina were attained several days earlier and declined as specific leaf weight increased. Chlorophyll and soluble protein continued to increase beyond the attainment of A(max), but were not accompanied by further increases in photosynthetic rates.Much of the fixed carbon in leaves is partitioned between starch and sucrose. Starch content of leaves as a percentage of dry weight at the end of an 11-hour photoperiod was taken as an indication of the potential energy reserve accumulated by the leaf. Starch levels were the same regardless of leaf age during the period from 0.3 A(max) to 7 days after attaining A(max). Respiratory and synthetic activity of leaves decreased considerably during the same period, suggesting that starch accumulation is not entirely controlled by the energy demands of the leaf.Sucrose content increased steadily during leaf expansion and was accompanied by corresponding increases in sucrose phosphate synthetase (EC 2.4.1.14) activity and translocation rates. Sucrose phosphate synthetase may have an important regulatory role in photosynthate partitioning and translocation.
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PMID:Carbon assimilation and translocation in soybean leaves at different stages of development. 1666 Apr 68

The control of photosynthetic starch/sucrose formation in leaves of soybean (Glycine max L. Merr.) cultivars was studied in relation to stage of plant development, photosynthetic photoperiod, and nitrogen source. At each sampling, leaf tissue was analyzed for starch content, activities of sucrose-metabolizing enzymes, and labeling of starch and sucrose (by (14)CO(2) assimilation) in isolated cells. In three of the four varieties tested, nodulated plants had lower leaf starch levels and higher activities of sucrose phosphate synthetase (SPS), and isolated mesophyll cells incorporated more carbon (percentage of total (14)CO(2) fixed) into sucrose and less into starch as compared to nonnodulated (nitrate-dependent) plants. The variation among cultivars and nitrogen treatments observed in the activity of SPS in leaf extracts was positively correlated with labeling of sucrose in isolated cells (r = 0.81) and negatively correlated with whole leaf starch content (r = -0.66). The results suggested that increased demand for assimilates by nodulated roots may be accommodated by greater partitioning of carbon into sucrose in the mesophyll cells. We have also confirmed the earlier report (Chatterton, Silvius 1979 Plant Physiol 64: 749-753) that photoperiod affects partitioning of fixed carbon into starch. Within two days of transfer of nodulated soybean Ransom plants from a 14-hour to a 7-hour photoperiod, leaf starch accumulation rates doubled, and this effect was associated with increased labeling of starch and decreased labeling of sucrose in isolated cells. Concurrently, activities of SPS, sucrose synthase, and uridine diphosphatase in leaves were decreased.Four nodulated soybean cultivars were grown to maturity in a greenhouse. Fully expanded leaves at the top of the canopy were sampled during vegetative growth (45 days), at flowering (79 days), and at mid-podfill (120 days). In general, activities of SPS and uridine-5'-diphosphatase were highest during vegetative growth, and they decreased during reproductive development, whereas activity of sucrose synthase and leaf starch content tended to increase. Leaf starch was negatively correlated with levels of SPS (r = -0.71). The results support the postulate that sucrose-P synthetase is a key control point regulating the photosynthetic formation of sucrose, and, hence, starch.
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PMID:Biochemical Basis for Partitioning of Photosynthetically Fixed Carbon between Starch and Sucrose in Soybean (Glycine max Merr.) Leaves. 1666 77

Experiments were conducted with vegetative soybean plants (Glycine max [L.] Merr., ;Ransom') to determine whether the activities in leaf extracts of key enzymes in sucrose metabolism changed during the daily light/dark cycle. The activity of sucrose-phosphate synthase (SPS) exhibited a distinct diurnal rhythm, whereas the activities of UDP-glucose pyrophosphorylase, cytoplasmic fructose-1,6-bisphosphatase, and sucrose synthase did not. The changes in extractable SPS activity were not related directly to photosynthetic rates or light/dark changes. Hence, it was postulated that the oscillations were under the control of an endogenous clock. During the light period, the activity of SPS was similar to the estimated rate of sucrose formation. In the dark, however, SPS activity declined sharply and then increased even though degradation of starch was linear. The activity of SPS always exceeded the estimated maximum rate of sucrose formation in the dark. Transfer of plants into light during the normal dark period (when SPS activity was low) resulted in increased partitioning of photosynthate into starch compared to partitioning observed during the normal light period. These results were consistent with the hypothesis that SPS activity in situ was a factor regulating the rate of sucrose synthesis and partitioning of fixed carbon between starch and sucrose in the light.
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PMID:Characterization of diurnal changes in activities of enzymes involved in sucrose biosynthesis. 1666 33

Experiments were conducted with soybean (Glycine max [L.] Merr. cv ;Ransom') plants to determine if diurnal rhythms in net carbon dioxide exchange rate (CER), stomatal resistance, and sucrose-phosphate synthase (SPS) activity persisted in constant environmental conditions (constant light, LL; constant dark DD) and to assess the importance of these rhythms to the production of nonstructural carbohydrates (starch, sucrose, and hexose). Rhythms in CER, stomatal resistance, and SPS activity were observed in constant environmental conditions but the rhythms differed in period length, amplitude, and phase. The results indicated that these photosynthetic parameters are not controlled in a coordinated manner. The activity of UDPG pyrophosphorylase, another enzyme involved in sucrose formation, did not fluctuate rhythmically in constant conditions but increased with time in plants in LL. In LL, the rhythm in CER was correlated positively with fluctuations in total chlorophyll (r = 0.810) and chlorophyll a (r = 0.791) concentrations which suggested that changes in pigment concentration were associated with, but not necessarily the underlying mechanism of, the rhythm in photosynthetic rate. Assimilate export rate, net starch accumulation rate, and leaf sucrose concentration also fluctuated in constant light. No single photosynthetic parameter was closely correlated with fluctuations in assimilate export during LL; thus, assimilate export may have been controlled by interactions among the endogenous rhythms in CER, SPS activity, or other metabolic factors which were not measured in the present study.
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PMID:Endogenous Rhythms in Photosynthesis, Sucrose Phosphate Synthase Activity, and Stomatal Resistance in Leaves of Soybean (Glycine max [L.] Merr.). 1666 41

Monoclonal antibodies specific for sucrose phosphate synthase (SPS; EC 2.4.1.14) have been obtained for the first time. Three independent clones have been isolated which inhibited spinach (Spinacia oleracea L.) leaf SPS activity and facilitated the enzyme purification by immunoprecipitation. All three clones were specific for the spinach enzyme but neither inhibited nor precipitated the SPS present in tissue extracts of maize (Zea mays L.), barley (Hordeum vulgare L.), soybean (Glycine max L.), and sugar beet (Beta vulgaris L.). The inhibition of SPS activity by all three clones was reversible in the presence of UDPG, suggesting the presence of an epitope at the substrate-binding site. Immunoprecipitates of active enzyme preparations consistently revealed the presence of a 120 kilodalton polypeptide, indicating that the enzyme may be a homotetramer with a native molecular weight of about 480 kilodaltons. The occasional appearance of a 52 kilodalton polypeptide in the immunoprecipitates of some enzyme preparations was not the result of proteolysis, was not necessary for enzyme activity, and did not contain an antigenic site as revealed by Western blotting experiments. All three antibodies bind weakly to the SDS denatured 120 kilodalton subunit bound to nitrocellulose. The specific activity of the purified spinach enzyme was determined for the first time to be approximately 150 units per milligram SPS protein (pH 7.5 and 25 degrees C) based on quantitative immunoprecipitation of the enzyme.
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PMID:Purification and preliminary characterization of sucrose-phosphate synthase using monoclonal antibodies. 1666 75

The effect of inorganic phosphate (Pi) on sucrose-phosphate synthase (SPS) activity was determined for the enzyme from five plant species (Nicotiana tabacum L., Spinacia oleracea L., Triticum aestivum L., Zea mays L., Glycine max L.) using two assay methods. The assay method based on determination of uridine diphosphate glucose- (UDPG) and fructose-6-phosphate-dependent sucrose formation was linear up to 15 minutes for all species tested. When assayed in this way, the effect of Pi at levels of 5 or 10 millimolar in the assay was variable, ranging from 0 to 35% inhibition of SPS activity. The assay method based on substrate dependent UDP formation was linear for some, but not for all of the species tested. Deviations from linearity were caused by loss of UDP from the assay medium. In some species, the extent of UDP loss was influenced by the level of Pi in the assay medium and, for at least one species (tobacco), it was influenced by the environment in which the plants were grown. The results indicated that (a) the role of Pi as an effector of SPS may vary depending on the species, and (b) the UDP assay method should be used with caution for assays of crude or desalted extracts, particularly when evaluating the effect of Pi on SPS activity.
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PMID:Species and Environmental Variations in the Effect of Inorganic Phosphate on Sucrose-Phosphate Synthase Activity : Reliability of Assays Based Upon UDP Formation. 1666 54

Several lines of evidence indicate that the partitioning of photosynthate between starch and sucrose is influenced by the relative concentrations of inorganic phosphate (Pi) in the cytosol and chloroplast. Two greenhouse experiments were conducted to determine the influence of long-term differences in soil P levels, ranging from deficient to supraoptimum, on leaf starch and sucrose concentrations, and activities of adenosine diphosphate glucose (ADPG) pyrophosphorylase and sucrose-phosphate synthase (SPS) during the grain filling period in soybean (Glycine max [L.] Merr.). It was hypothesized that, compared with optimum P nutrition, leaf starch and sucrose concentrations would be increased and decreased, respectively, for P deficiency and visa versa for supraoptimum P nutrition. Relative to the optimum soil P level, leaf Pi concentration was not altered by P deficiency but was increased two- to fourfold for the supraoptimum soil P treatment. The concentrations of leaf starch and sucrose were not markedly affected by any of the P fertility treatments and were not closely related to the activities of ADPG pyrophosphorylase and SPS. P deficiency resulted in increased activity of both enzymes in one of the experiments. The results indicated that long-term soil P treatments, that caused either large decreases in plant growth (P deficiency) or large increases in leaf Pi concentration (supraoptimum P), did not markedly alter starch and sucrose metabolism. Furthermore, it can be inferred that the method of plant culture and/or imposition of the P treatments is a critical factor in interpreting results of P nutrition studies.
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PMID:Phosphorus Nutrition Influence on Starch and Sucrose Accumulation, and Activities of ADP-Glucose Pyrophosphorylase and Sucrose-Phosphate Synthase during the Grain Filling Period in Soybean. 1666 37

Net photosynthesis (CER), assimilate-export rate, sucrose-phosphate-synthase (EC 2.4.1.14) activity, fructose-2,6-bisphosphate content, and 6-phosphofructo-2-kinase (EC 2.7.1.105) activity were monitored in leaves of soybean (Glycine max (L.) Merr.) plants during a 12:12 h day-night cycle, and in plants transferred, at regular intervals throughout the diurnal cycle, to an illuminated chamber for 3 h. In the control plants, assimilate-export rate decreased progressively during the day whereas in transferred plants, a strongly rhythmic fluctuation in both CER and export rate was observed over the 24-h test period. Two maxima during the 24-h period for both processes were observed: one when plants were transferred during the middle of the normal light period, and a second when plants were transferred during the middle of the normal dark period. Overall, the results indicated that export rate was correlated positively with photosynthetic rate and sucrose-phosphate-synthase activity, and correlated negatively with fructose-2,6-bisphosphate levels, and that coarse control and fine control of the sucrose-formation pathway are coordinated during the diurnal cycle. Diurnal changes in sucrose-phosphate-synthase activity were not associated with changes in regulatory properties (phosphate inhibition) or substrate affinities. The biochemical basis for the diurnal rhythm in sucrose-phosphate-synthase activity in the soybean leaf thus appears to involve changes in the amount of the enzyme or a post-translational modification that affects only the maximum velocity.
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PMID:Coordinate control of sucrose formation in soybean leaves by sucrose-phosphate synthase and fructose-2,6-bisphosphate. 2423 78

Two forms of sucrose-phosphate synthase (EC 2.4.1.14) were resolved from leaves of three species, maize (Zea mays L. cv. Pioneer 3184), soybean (Glycine max (L.) Merr., cv. Ransom) and spinach (Spinacia oleracea L. cv. Resistoflay) by hydroxyapatite Ultrogel chromatography, using a 75-mM (designated peak 1) and 250-mM (peak 2) K-phosphate discontinuous-gradient elution. Rechromatography of the two forms showed that they were not readily interconvertible. The distribution of activity between the two forms differed among species and changed during purification of the enzyme. Recovery of peak-1 activity was specifically lowered when maize leaf extracts were prepared in the absence of magnesium, indicating that the two forms may differ in stability. In addition, the forms of the enzyme from maize differed in the extent of glucose-6-phosphate activation. These results provide evidence for the existence of multiple forms of sucrose-phosphate synthase in leaves of different species and that the forms differ in regulatory properties.
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PMID:Resolution of two molecular forms of sucrose-phosphate synthase from maize, soybean and spinach leaves. 2423 14


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