Asymmetric Labelling of Maltose during Photosynthesis in 14CO2

Linden, James C.; Schilling, Norbert; Brackenhofer, H.; Kandler, Otto

doi:10.1016/s0044-328x(75)80035-3

Cited by 27 publications

(11 citation statements)

References 12 publications

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“…Mutagenesis of AGPase to promote in vivo activity led to an increase in maltose levels in the light (Hädrich et al, 2012). 14 CO 2 labeling studies of spinach chloroplasts detected very-short-term labeling of maltose from 14 CO 2 (Linden et al, 1975;Schilling, 1982;Linden and Schilling, 1984). As this molecule was asymmetrically labeled, its formation cannot be attributed to the action of b-amylase on starch.…”

Section: Discussionmentioning

confidence: 97%

Metabolic Fluxes in an Illuminated Arabidopsis Rosette

et al. 2013

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Photosynthesis is the basis for life, and its optimization is a key biotechnological aim given the problems of population explosion and environmental deterioration. We describe a method to resolve intracellular fluxes in intact Arabidopsis thaliana rosettes based on time-dependent labeling patterns in the metabolome. Plants photosynthesizing under limiting irradiance and ambient CO 2 in a custom-built chamber were transferred into a 13 CO 2 -enriched environment. The isotope labeling patterns of 40 metabolites were obtained using liquid or gas chromatography coupled to mass spectrometry. Labeling kinetics revealed striking differences between metabolites. At a qualitative level, they matched expectations in terms of pathway topology and stoichiometry, but some unexpected features point to the complexity of subcellular and cellular compartmentation. To achieve quantitative insights, the data set was used for estimating fluxes in the framework of kinetic flux profiling. We benchmarked flux estimates to four classically determined flux signatures of photosynthesis and assessed the robustness of the estimates with respect to different features of the underlying metabolic model and the time-resolved data set.

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Section: Discussionmentioning

confidence: 97%

Metabolic Fluxes in an Illuminated Arabidopsis Rosette

et al. 2013

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“…Maltase is also apparently lacking in pea chloroplasts (20). Instead, maltose may be degraded by maltose phosphorylase (22,33) which has been observed in pea chloroplasts (20). It is conceivable that maltose, like glucose, might be transported to the cytoplasm where it could be converted to glucose by cytoplasmic localized maltase activity.…”

Section: Discussionmentioning

confidence: 99%

Subcellular Localization of the Starch Degradative and Biosynthetic Enzymes of Spinach Leaves

Okita

Greenberg²,

Kuhn³

et al. 1979

Plant Physiol.

140

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The subceflular localization of the starch biosynthetic and degradative enzymes of spinach leaves was carried out by measuring the distribution of the enzymes in a crude chloroplast pellet and soluble protein fraction, and by the separation on sucrose density gradients of intact organelles, chhoroplasts, peroxisomes, and mitochondria of a protoplast lysate. ADPGlucose pyropbosphorylase, starch synthase, and starch-branching enzymes are quantitatively associated with the chloroplasts. The starch degradative enzymes amylase, R-enzyme (debranching activity), phosphorylase, and D-enzyme (transglycosyhse) are observed both in the chloroplast and soluble protein fractions, the bulk of the degradative enzyme activities reside in the latter fraction Chromatography of a chloroplast extract on diethylaminoethyl-ceilulose resolves the R-and D-enzymes from amylase and phosphorylase activities although the two latter enzyme activities coeluted. The digestion pattern of amylase with amyopectin as a substrate indicates an endolytic activity but displays properties unlike the typical a-amylase as isolated from endosperm tissue.

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“…Maltose occurs in only small amounts in leaves (18) but has been detected as a "C-labeled product of "4CO2 assimilation in several species (9,19,20,22,23,30). Herold, McGee, and Lewis (13) reported greatly enhanced incorporation of 14C from 14CO2 into maltose in sugar beet (Beta vulgaris L.) when leaf discs were preincubated in mannose solution.…”

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confidence: 99%

Accumulation of Maltose during Photosynthesis in Protoplasts Isolated from Spinach Leaves Treated with Mannose

Herold

Leegood²,

McNeil³

et al. 1981

Plant Physiol.

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When mannose was included in the enzyme incubation medium during the preparation of protoplasts from leaves of spinach, maltose was an early product of protoplast photosynthesis and, after 12 minutes, accounted for up to 15% of the 'C incorporated from 'CO2. Maltose was not detected in protoplasts prepared in the normal enzyme medium. Rapid separation of cytoplasm and chloroplasts following exposure to "CO2 showed that maltose was present in both fractions. Direct measurements of [I4Clmaltose uptake indicated transport across the chloroplast envelope at rates similar to the transport of glucose. The source of maltose and site of its initial formation are discussed.Maltose occurs in only small amounts in leaves (18) but has been detected as a "C-labeled product of "4CO2 assimilation in several species (9,19,20,22,23,30 Photosynthetic Carbon Assimilation. Protoplasts were added to a medium containing 500 mm sorbitol, 1 mm CaC12, 25 mm Tricine (pH 7.6), and 5 mm NaH14CO3 (20 Ci/mol) to give 50 ,ug Chl/ml.The mixture was illuminated in an O2 electrode (5) at 20 C and photosynthesis was measured by 02 evolution and by incorporation of 14C (below). The reaction was terminated by the addition of boiling absolute ethanol to give a final concentration of 801% (v/v). This total extract was centrifuged, and the pellet reextracted twice in 80%1o ethanol and twice in warm H20 to give an ethanol/ H20-soluble fraction (13). The remaining pellet was incubated with amyloglucosidase solution (3), and the starch content was estimated by release of ['4C]glucose. Samples of the total extract, the ethanol/H20-soluble fraction, and the supernatant following amyloglucosidase digestion ofthe pellet were counted on planchets using a Nuclear Chicago gas flow counter, together with appropriate standards. Free sugars and a base line component (which includes charged compounds and oligosaccharides) in the ethanol/ H20-soluble extract, and glucose in the amyloglucosidase extract were separated by paper chromatography in ethyl acetate-pyridine-H20 (8:2:1, v/v) and radioactivity was determined with a Berthold LB 280 scanner. In addition to the earlier methods used for maltose identification (13), extracts were heated with borohydride which reduces maltose to maltitol (18), followed by maltase treatment. Maltitol, sorbitol, and glucose released from it by maltase were identified by chromatography against "4C-labeled standards and by GLC. The identity of sucrose was confirmed as before (26).Protoplast Fractionation. Protoplasts were incubated in a medium containing 400 mm sorbitol, 1 mm CaCl2, 25 mm Tricine (pH 7.6), and 5 mm NaH'4C03 (60 Ci/mol). Protoplasts were illuminated and photosynthesis was measured by 02 evolution and 14C incorporation (27). After 12 min illumination, or at 2-min intervals for time-course experiments, 1OO-AtL protoplast samples of extract (5 jig Chl) were taken and the chloroplastic and cytoplasmic fractions were rapidly separated by centrifugation filtration through nylon mesh and silicone oil 19:1), using the ...

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Asymmetric Labelling of Maltose during Photosynthesis in 14CO2

Cited by 27 publications

References 12 publications

Metabolic Fluxes in an Illuminated Arabidopsis Rosette

Metabolic Fluxes in an Illuminated Arabidopsis Rosette

Subcellular Localization of the Starch Degradative and Biosynthetic Enzymes of Spinach Leaves

Accumulation of Maltose during Photosynthesis in Protoplasts Isolated from Spinach Leaves Treated with Mannose

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