Pyrophosphorylases in <i>Solanum tuberosum</i>

Sowokinos, Joseph R.

doi:10.1104/pp.57.1.63

Cited by 110 publications

(38 citation statements)

References 25 publications

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“…coarse metabolic control) is one level of regulation affecting starch synthesis in developing reserve tissues. Increases in both ADPglucose pyrophosphorylase (27,29,30) and starch synthase (ADPglucose specific [1,20]) have been correlated with increased rates of starch accumulation in barley, peas, wheat, maize endosperm, and potatoes during development. Among these nonchlorophyllous tissues, ADPglucose pyrophosphorylase from maize (4, 10) and potatoes (28) have been studied in detail in regard to their catalytic regulation by 3-P-glycerate and Pi (ie.…”

Section: Resultsmentioning

confidence: 99%

“…The physiological importance of the potato tuber's ADPglucose pyrophosphorylase sensitivity towards the allosteric effectors 3-P-glycerate and Pi may take on added significance in view of the above findings. The potato enzyme has been suggested to be closely associated with/or located inside the amyloplast of potato cells which is the site of starch synthesis (27 …”

Section: Resultsmentioning

confidence: 99%

“…The potato variety Norchip (Solanum tuberosum L.) was used as the source of enzyme during the course of this study. Acetone powders were prepared from immature tubers (200 g average size) as previously described (27). Two hundred g fresh tissue, selected at random from five healthy tubers, were thinly sliced and immediately frozen with Dry Ice.…”

Section: Methodsmentioning

confidence: 99%

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Pyrophosphorylases in Solanum tuberosum

Sowokinos

Preiss²

1982

Plant Physiol.

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141

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ADPglucose pyrophosphorylase from potato (Solanum tuberosum L.) tubers has been purified by hydrophobic chromatography on 3 aminopropylsepharose (Seph-C3-NH2). The purified preparation showed two closely associated protein-staining bands that coincided with enzyme activity stains. Only one major protein staining band was observed in sodium dodecyl sulfate polyacrylamide gel electrophoresis. The subunit molecular weight was determined to be 50,000. The molecular weight of the native enzyme was determined to be 200,000. The enzyme appeared to be a tetramer consisting of subunits of the same molecular weight. The subunit molecular weight of the enzyme is compared with previously reported subunit molecular weights of ADPglucose pyrophosphorylases from spinach leaf, maize endosperm, and various bacteria. ADPglucose synthesis from ATP and glucose 1-P is almost completely dependent on the presence of 3-P-glycerate and is inhibited by inorganic phosphate. The kinetic constants for the substrates and Mg2+ are reported. The enzyme V,,. is stimulated about 1.5-to 3-fold by 3 millimolar DTT. The significance of the activation by 3-P-glycerate and inhibition by inorganic phosphate ADPglucose synthesis catalyzed by the potato tuber enzyme is discussed.The enzyme ADPglucose pyrophosphorylase (ATP:ca-glucose-I-P adenylyltransferase, E.C. 2.7.7.27), is one of the main regulatory steps in the biosynthesis of a-glucans in bacteria and plants (21,22). This enzyme catalyzes the reversible reaction seen below:ATP + glucose-l-P , ADPglucose + PPi Its regulatory and catalytic properties from several sources have been recently reviewed (22). ADPglucose pyrophosphorylases from leaves of higher plants (23, 24) and nonchlorophyllous reserve tissues (4, 28) are allosterically activated and inhibited by 3-P-glycerate and Pi, respectively. The extensively studied enzyme in maize endosperm (4, 10) is less sensitive to these effectors than those studied in chlorophyllous leaf tissues (24). However, the '

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Pyrophosphorylases in Solanum tuberosum

Sowokinos

Preiss²

1982

Plant Physiol.

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141

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“…Insoluble matter was removed by centrifugation at 38,000g for 10 min and an aliquot of the extract was desalted by passage through a small column of Sephadex G-25. Assay procedures for SPS (23), cytoplasmic fructose bisphosphatase (23), starch synthase (5), UDP-glucose pyrophosphorylase (27), ADP-glucose pyrophosphorylase (27), and invertase (13) (10). This may represent a case of a single locus gene duplication as has been suggested for anomalous isozyme patterns in other species (10).…”

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confidence: 96%

Alterations in Growth, Photosynthesis, and Respiration in a Starchless Mutant of Arabidopsis thaliana (L.) Deficient in Chloroplast Phosphoglucomutase Activity

Caspar¹,

Huber²,

Somerville³

1985

Plant Physiol.

497

561

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(12,23,28).The effect of carbohydrate accumulation on the rate of dark respiration has received less attention but appears to have been consistently observed by a variety of approaches (2,6,29). The essential observation is that the rate of respiration is proportional to carbohydrate content or is stimulated by provision of exogenous carbohydrate. The implication is that the amount of respiration is regulated by substrate supply rather than demand for ATP or reducing equivalents. Indeed, it has been suggested that, under conditions of high carbohydrate supply, a substantial proportion of the reductant generated during carbohydrate catabolism may be consumed by the alternative oxidase without being linked to ATP production (3,15

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“…The homogenate was centrifuged in a microcentrifuge (model 235, Fisher Scientific) at maximum speed (approximately 12,000g) for 3 min at 4°C. The supernatant was desalted through a small Sephadex G-25 (superfine) column before assaying for AGPase activity, according to the method of Sowokinos (1976). AGPase activities of the desalted leaf extracts were assayed at 37°C in a reaction mixture containing 80 mm glycylglycine, pH 7.5, 5 mm MgCl 2 , 10 mm NaF, 2.5 mm DTT, 0.5 mm NADP, 1 unit of phosphoglucomutase, 1 unit of Glc-6-P dehydrogenase, 2 mm ADP-Glc, 4 mm 3-PGA, and 1.5 mm sodium pyrophosphate.…”

Section: Enzyme Extraction and Assaymentioning

confidence: 99%

Modification of Carbon Partitioning, Photosynthetic Capacity, and O2 Sensitivity in Arabidopsis Plants with Low ADP-Glucose Pyrophosphorylase Activity1

Okita²,

1999

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Wild-type Arabidopsis plants, the starch-deficient mutant TL46, and the near-starchless mutant TL25 were evaluated by noninvasive in situ methods for their capacity for net CO 2 assimilation, true rates of photosynthetic O 2 evolution (determined from chlorophyll fluorescence measurements of photosystem II), partitioning of photosynthate into sucrose and starch, and plant growth. Compared with wild-type plants, the starch mutants showed reduced photosynthetic capacity, with the largest reduction occurring in mutant TL25 subjected to high light and increased CO 2 partial pressure. The extent of stimulation of CO 2 assimilation by increasing CO 2 or by reducing O 2 partial pressure was significantly less for the starch mutants than for wild-type plants. Under high light and moderate to high levels of CO 2 , the rates of CO 2 assimilation and O 2 evolution and the percentage inhibition of photosynthesis by low O 2 were higher for the wild type than for the mutants. The relative rates of 14 CO 2 incorporation into starch under high light and high CO 2 followed the patterns of photosynthetic capacity, with TL46 showing 31% to 40% of the starch-labeling rates of the wild type and TL25 showing less than 14% incorporation. Overall, there were significant correlations between the rates of starch synthesis and CO 2 assimilation and between the rates of starch synthesis and cumulative leaf area. These results indicate that leaf starch plays an important role as a transient reserve, the synthesis of which can ameliorate any potential reduction in photosynthesis caused by feedback regulation.Because plant productivity is governed by photosynthetic activity and sink activity for utilizing photosynthate (see Zamski and Schaffer, 1996), it is important to understand the environmental and genetic factors affecting these processes. In general, photosynthesis is limited mainly by light harvesting and assimilatory power under low light and by carboxylation and photorespiration under low CO 2 . Under saturating light and CO 2 , however, photosynthesis may be controlled by processes that convert triose-P into starch and Suc (Sage, 1990(Sage, , 1994Stitt, 1996). Thus, the capacity to utilize triose-P for carbohydrate synthesis can establish an upper limit for the maximum rate of photosynthesis under CO 2 -and light-saturated conditions (Sage, 1990;Sharkey et al., 1995). This is clearly demonstrated under certain conditions by the response of photosynthesis of C 3 plants to low O 2 . In many instances, the increase in CO 2 assimilation attributable to the reduction in photorespiration under low O 2 can be predicted accurately based on the known kinetic properties of Rubisco. However, when the extent of stimulation of photosynthesis by C 3 plants under subatmospheric O 2 is less than predicted, or when there is reversed O 2 sensitivity, photosynthesis is considered to be feedback limited as a result of restrictions on triose-P utilization (Sharkey, 1985; Leegood and Furbank, 1986;Sage and Sharkey, 1987; Hanson, 1990;Sun et al., 1997). L...

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Pyrophosphorylases in Solanum tuberosum

Cited by 110 publications

References 25 publications

Pyrophosphorylases in Solanum tuberosum

Pyrophosphorylases in Solanum tuberosum

Alterations in Growth, Photosynthesis, and Respiration in a Starchless Mutant of Arabidopsis thaliana (L.) Deficient in Chloroplast Phosphoglucomutase Activity

Modification of Carbon Partitioning, Photosynthetic Capacity, and O2 Sensitivity in Arabidopsis Plants with Low ADP-Glucose Pyrophosphorylase Activity1

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